From 009e5f4e0f3f01d2abed0b04096a3fe3cfbb5540 Mon Sep 17 00:00:00 2001
From: Jarry Shaw <jarryshaw@icloud.com>
Date: Thu, 8 Oct 2026 09:51:32 -0400
Subject: [PATCH] fix(mh): keep the reserved bits of 24 BitField flag
 namespaces on rebuild

Ten messages (BRM, FBack, FBU, FB, HAck, HI, Heartbeat, LRA, SR, UPN),
twelve options (DNS-UPDATE, DMNP, DynIP Multicast Selector, IPv4 Address
Ack, IPv4 DHCP Support Mode, IPv4 HoA Reply/Request, IPv4 Traffic
Offload Selector, MAG Multipath Binding, NAT Detection, Redirect,
Transient Binding), the Multi-Prefix CGA extension and the per-session
bit-rate QoS attribute left bits of their flags word unnamed, so they
were packed back as zero.

Each site now names a 'reserved' sub-field, read into the data model
(flags_reserved on messages, reserved elsewhere) and written by make(),
defaulting to 0.

Closes #1418
Refs #1288
---
 pcapkit/protocols/data/internet/mh.py         |  96 +++++++--
 pcapkit/protocols/internet/mh.py              | 130 +++++++++++-
 pcapkit/protocols/schema/internet/mh.py       |  45 ++++
 .../internet/test_mh_flags_reserved_unit.py   | 192 ++++++++++++++++++
 tests/protocols/internet/test_mh_unit.py      |  32 +--
 5 files changed, 446 insertions(+), 49 deletions(-)
 create mode 100644 tests/protocols/internet/test_mh_flags_reserved_unit.py

diff --git a/pcapkit/protocols/data/internet/mh.py b/pcapkit/protocols/data/internet/mh.py
index a36e950231..7a971715f4 100644
--- a/pcapkit/protocols/data/internet/mh.py
+++ b/pcapkit/protocols/data/internet/mh.py
@@ -357,6 +357,8 @@ class FastBindingUpdateMessage(MH):
     lla_compat: 'bool'
     #: Key management mobility capability flag.
     key_mngt: 'bool'
+    #: Reserved bits, i.e. the 12 bits after the ``K`` flag.
+    flags_reserved: 'int'
     #: Lifetime. :rfc:`5568#section-6.2.2` counts this in seconds rather than in
     #: the units of 4 seconds the binding messages use.
     lifetime: 'timedelta'
@@ -366,6 +368,7 @@ class FastBindingUpdateMessage(MH):
     if TYPE_CHECKING:
         def __init__(self, next: 'TransType', length: 'int', type: 'Packet', reserved: 'int', chksum: 'bytes',
                      seq: 'int', ack: 'bool', home: 'bool', lla_compat: 'bool', key_mngt: 'bool',
+                     flags_reserved: 'int',
                      lifetime: 'timedelta', options: 'OrderedMultiDict[Enum_Option, Option]') -> 'None': ...
 
 
@@ -381,6 +384,8 @@ class FastBindingAcknowledgmentMessage(MH):
     status: 'FastBindingAcknowledgmentStatus'
     #: Key management mobility capability flag.
     key_mngt: 'bool'
+    #: Reserved bits, i.e. the seven bits after the ``K`` flag.
+    flags_reserved: 'int'
     #: Sequence number.
     seq: 'int'
     #: Lifetime. :rfc:`5568#section-6.2.3` counts this in seconds rather than in
@@ -391,7 +396,8 @@ class FastBindingAcknowledgmentMessage(MH):
 
     if TYPE_CHECKING:
         def __init__(self, next: 'TransType', length: 'int', type: 'Packet', reserved: 'int', chksum: 'bytes',
-                     status: 'FastBindingAcknowledgmentStatus', key_mngt: 'bool', seq: 'int',
+                     status: 'FastBindingAcknowledgmentStatus', key_mngt: 'bool',
+                     flags_reserved: 'int', seq: 'int',
                      lifetime: 'timedelta',
                      options: 'OrderedMultiDict[Enum_Option, Option]') -> 'None': ...
 
@@ -434,6 +440,8 @@ class HandoverInitiateMessage(MH):
     proxy: 'bool'
     #: Forwarding flag.
     forward: 'bool'
+    #: Reserved bits, i.e. the four bits after the ``F`` flag.
+    flags_reserved: 'int'
     #: Code.
     code: 'Enum_HandoverInitiateStatus'
     #: Mobility options.
@@ -442,6 +450,7 @@ class HandoverInitiateMessage(MH):
     if TYPE_CHECKING:
         def __init__(self, next: 'TransType', length: 'int', type: 'Packet', reserved: 'int', chksum: 'bytes',
                      seq: 'int', assign: 'bool', buffer: 'bool', proxy: 'bool', forward: 'bool',
+                     flags_reserved: 'int',
                      code: 'Enum_HandoverInitiateStatus',
                      options: 'OrderedMultiDict[Enum_Option, Option]') -> 'None': ...
 
@@ -458,6 +467,8 @@ class HandoverAcknowledgeMessage(MH):
     proxy: 'bool'
     #: Forwarding flag.
     forward: 'bool'
+    #: Reserved bits, i.e. the five bits after the ``F`` flag.
+    flags_reserved: 'int'
     #: Code.
     code: 'Enum_HandoverACKStatus'
     #: Mobility options.
@@ -465,7 +476,7 @@ class HandoverAcknowledgeMessage(MH):
 
     if TYPE_CHECKING:
         def __init__(self, next: 'TransType', length: 'int', type: 'Packet', reserved: 'int', chksum: 'bytes',
-                     seq: 'int', buffer: 'bool', proxy: 'bool', forward: 'bool',
+                     seq: 'int', buffer: 'bool', proxy: 'bool', forward: 'bool', flags_reserved: 'int',
                      code: 'Enum_HandoverACKStatus',
                      options: 'OrderedMultiDict[Enum_Option, Option]') -> 'None': ...
 
@@ -479,6 +490,8 @@ class HeartbeatMessage(MH):
     unsolicited: 'bool'
     #: Response flag. Unset for a Heartbeat request, set for a response.
     response: 'bool'
+    #: Reserved bits, i.e. the 14 bits before the ``U`` flag.
+    flags_reserved: 'int'
     #: Sequence number.
     seq: 'int'
     #: Mobility options.
@@ -486,7 +499,7 @@ class HeartbeatMessage(MH):
 
     if TYPE_CHECKING:
         def __init__(self, next: 'TransType', length: 'int', type: 'Packet', reserved: 'int', chksum: 'bytes',
-                     unsolicited: 'bool', response: 'bool', seq: 'int',
+                     unsolicited: 'bool', response: 'bool', flags_reserved: 'int', seq: 'int',
                      options: 'OrderedMultiDict[Enum_Option, Option]') -> 'None': ...
 
 
@@ -530,6 +543,8 @@ class BindingRevocationMessage(MH):
     ipv4_hoa: 'bool'
     #: Global revocation flag.
     global_revocation: 'bool'
+    #: Reserved bits, i.e. the 13 bits after the ``G`` flag.
+    flags_reserved: 'int'
     #: Mobility options.
     options: 'OrderedMultiDict[Enum_Option, Option]'
 
@@ -537,7 +552,7 @@ class BindingRevocationMessage(MH):
         def __init__(self, next: 'TransType', length: 'int', type: 'Packet', reserved: 'int', chksum: 'bytes',
                      br_type: 'Enum_BindingRevocation',
                      code: 'Enum_RevocationTrigger | Enum_RevocationStatusCode', seq: 'int',
-                     proxy: 'bool', ipv4_hoa: 'bool', global_revocation: 'bool',
+                     proxy: 'bool', ipv4_hoa: 'bool', global_revocation: 'bool', flags_reserved: 'int',
                      options: 'OrderedMultiDict[Enum_Option, Option]') -> 'None': ...
 
 
@@ -567,6 +582,8 @@ class LocalizedRoutingAcknowledgmentMessage(MH):
     seq: 'int'
     #: Unsolicited flag.
     unsolicited: 'bool'
+    #: Reserved bits, i.e. the seven bits after the ``U`` flag.
+    flags_reserved: 'int'
     #: Status. :rfc:`6705#section-10.2` defines its values inline with no IANA
     #: registry behind them, so this field carries the module-local
     #: :class:`~pcapkit.protocols.internet.mh.LocalizedRoutingStatus` rather than
@@ -579,7 +596,7 @@ class LocalizedRoutingAcknowledgmentMessage(MH):
 
     if TYPE_CHECKING:
         def __init__(self, next: 'TransType', length: 'int', type: 'Packet', reserved: 'int', chksum: 'bytes',
-                     seq: 'int', unsolicited: 'bool', status: 'LocalizedRoutingStatus',
+                     seq: 'int', unsolicited: 'bool', flags_reserved: 'int', status: 'LocalizedRoutingStatus',
                      lifetime: 'timedelta',
                      options: 'OrderedMultiDict[Enum_Option, Option]') -> 'None': ...
 
@@ -596,13 +613,15 @@ class UpdateNotificationMessage(MH):
     ack: 'bool'
     #: Retransmission flag.
     retransmit: 'bool'
+    #: Reserved bits, i.e. the 14 bits after the ``D`` flag.
+    flags_reserved: 'int'
     #: Mobility options.
     options: 'OrderedMultiDict[Enum_Option, Option]'
 
     if TYPE_CHECKING:
         def __init__(self, next: 'TransType', length: 'int', type: 'Packet', reserved: 'int', chksum: 'bytes',
                      seq: 'int', reason: 'Enum_UpdateNotificationReason', ack: 'bool',
-                     retransmit: 'bool',
+                     retransmit: 'bool', flags_reserved: 'int',
                      options: 'OrderedMultiDict[Enum_Option, Option]') -> 'None': ...
 
 
@@ -642,6 +661,8 @@ class FlowBindingMessage(MH):
     #: Acknowledgement requested flag. Only meaningful in an indication; an
     #: acknowledgement reserves the whole octet this bit is taken from.
     ack: 'bool'
+    #: Reserved bits, i.e. the seven bits after the ``A`` flag.
+    flags_reserved: 'int'
     #: Mobility options.
     options: 'OrderedMultiDict[Enum_Option, Option]'
 
@@ -649,7 +670,7 @@ class FlowBindingMessage(MH):
         def __init__(self, next: 'TransType', length: 'int', type: 'Packet', reserved: 'int', chksum: 'bytes',
                      fb_type: 'Enum_FlowBindingType', seq: 'int',
                      code: 'Enum_FlowBindingIndicationTrigger | Enum_FlowBindingACKStatus',
-                     ack: 'bool',
+                     ack: 'bool', flags_reserved: 'int',
                      options: 'OrderedMultiDict[Enum_Option, Option]') -> 'None': ...
 
 
@@ -677,12 +698,14 @@ class SubscriptionResponseMessage(MH):
     #: Multicast information flag, set when the response carries active
     #: multicast subscription options.
     info: 'bool'
+    #: Reserved bits, i.e. the seven bits after the ``I`` flag.
+    flags_reserved: 'int'
     #: Mobility options.
     options: 'OrderedMultiDict[Enum_Option, Option]'
 
     if TYPE_CHECKING:
         def __init__(self, next: 'TransType', length: 'int', type: 'Packet', reserved: 'int', chksum: 'bytes',
-                     seq: 'int', info: 'bool',
+                     seq: 'int', info: 'bool', flags_reserved: 'int',
                      options: 'OrderedMultiDict[Enum_Option, Option]') -> 'None': ...
 
 
@@ -880,11 +903,14 @@ class MultiPrefixExtension(CGAExtension):
     #: P flag. Set if a public key is included in the Public Key field of
     #: the CGA Parameter Data Structure, reset otherwise.
     flag: 'bool'
+    #: Reserved bits, i.e. the 31 bits after the ``P`` flag.
+    reserved: 'int'
     #: Prefixes.
     prefixes: 'tuple[int, ...]'
 
     if TYPE_CHECKING:
-        def __init__(self, type: 'Enum_CGAExtension', length: 'int', flag: 'bool', prefixes: 'tuple[int, ...]') -> 'None': ...
+        def __init__(self, type: 'Enum_CGAExtension', length: 'int', flag: 'bool', reserved: 'int',
+                     prefixes: 'tuple[int, ...]') -> 'None': ...
 
 
 @info_final
@@ -1106,13 +1132,15 @@ class DNSUpdateOption(Option):
     #: Remove flag. Set when the mobile node asks the home agent to remove the
     #: DNS entry rather than to create or update it.
     remove: 'bool'
+    #: Reserved bits, i.e. the seven bits after the ``R`` flag.
+    reserved: 'int'
     #: Mobile node identity, in FQDN form. Kept as :obj:`bytes` because the RFC
     #: does not say which of the two FQDN encodings is meant.
     identity: 'bytes'
 
     if TYPE_CHECKING:
         def __init__(self, type: 'Enum_Option', length: 'int', status: 'Enum_DNSStatusCode',
-                     remove: 'bool', identity: 'bytes') -> 'None': ...
+                     remove: 'bool', reserved: 'int', identity: 'bytes') -> 'None': ...
 
 
 @info_final
@@ -1174,12 +1202,14 @@ class IPv4AddressAcknowledgementOption(Option):
     #: Allocated prefix length. Meaningful only on success, and required to be
     #: zero on failure.
     prefix_length: 'int'
+    #: Reserved bits, i.e. the two bits after the prefix length.
+    reserved: 'int'
     #: Assigned IPv4 home address.
     address: 'IPv4Address'
 
     if TYPE_CHECKING:
         def __init__(self, type: 'Enum_Option', length: 'int',
-                     status: 'Enum_DSMIPv6HomeAddress', prefix_length: 'int',
+                     status: 'Enum_DSMIPv6HomeAddress', prefix_length: 'int', reserved: 'int',
                      address: 'IPv4Address') -> 'None': ...
 
 
@@ -1189,12 +1219,14 @@ class NATDetectionOption(Option):
 
     #: Force UDP encapsulation flag.
     force: 'bool'
+    #: Reserved bits, i.e. the 15 bits after the ``F`` flag.
+    reserved: 'int'
     #: Suggested NAT binding refresh interval, in seconds. ``0`` means the value
     #: is to be ignored, and all ones that no keep-alives are needed.
     refresh: 'timedelta'
 
     if TYPE_CHECKING:
-        def __init__(self, type: 'Enum_Option', length: 'int', force: 'bool',
+        def __init__(self, type: 'Enum_Option', length: 'int', force: 'bool', reserved: 'int',
                      refresh: 'timedelta') -> 'None': ...
 
 
@@ -1250,12 +1282,14 @@ class IPv4HomeAddressRequestOption(Option):
 
     #: Prefix length of the requested home network.
     prefix_length: 'int'
+    #: Reserved bits, i.e. the ten bits after the prefix length.
+    reserved: 'int'
     #: Requested IPv4 home address. ``0.0.0.0`` asks the local mobility anchor to
     #: allocate one.
     address: 'IPv4Address'
 
     if TYPE_CHECKING:
-        def __init__(self, type: 'Enum_Option', length: 'int', prefix_length: 'int',
+        def __init__(self, type: 'Enum_Option', length: 'int', prefix_length: 'int', reserved: 'int',
                      address: 'IPv4Address') -> 'None': ...
 
 
@@ -1268,12 +1302,14 @@ class IPv4HomeAddressReplyOption(Option):
     status: 'Enum_HomeAddressReply'
     #: Prefix length of the assigned home network.
     prefix_length: 'int'
+    #: Reserved bits, i.e. the two bits after the prefix length.
+    reserved: 'int'
     #: Assigned IPv4 home address.
     address: 'IPv4Address'
 
     if TYPE_CHECKING:
         def __init__(self, type: 'Enum_Option', length: 'int', status: 'Enum_HomeAddressReply',
-                     prefix_length: 'int', address: 'IPv4Address') -> 'None': ...
+                     prefix_length: 'int', reserved: 'int', address: 'IPv4Address') -> 'None': ...
 
 
 @info_final
@@ -1294,10 +1330,12 @@ class IPv4DHCPSupportModeOption(Option):
     #: DHCP support mode. Unset means the mobile access gateway acts as a DHCP
     #: relay, set that it acts as a DHCP server.
     mode: 'Enum_DHCPSupportMode'
+    #: Reserved bits, i.e. the 15 bits before the ``S`` flag.
+    reserved: 'int'
 
     if TYPE_CHECKING:
         def __init__(self, type: 'Enum_Option', length: 'int',
-                     mode: 'Enum_DHCPSupportMode') -> 'None': ...
+                     mode: 'Enum_DHCPSupportMode', reserved: 'int') -> 'None': ...
 
 
 @info_final
@@ -1360,12 +1398,14 @@ class TransientBindingOption(Option):
 
     #: Late path switch flag.
     late: 'bool'
+    #: Reserved bits, i.e. the seven bits before the ``L`` flag.
+    reserved: 'int'
     #: Maximum lifetime of the transient state. Counted on the wire in units of
     #: 100 milliseconds.
     lifetime: 'timedelta'
 
     if TYPE_CHECKING:
-        def __init__(self, type: 'Enum_Option', length: 'int', late: 'bool',
+        def __init__(self, type: 'Enum_Option', length: 'int', late: 'bool', reserved: 'int',
                      lifetime: 'timedelta') -> 'None': ...
 
 
@@ -1496,10 +1536,12 @@ class RedirectOption(Option):
     ipv6: 'Optional[IPv6Address]'
     #: IPv4 address of the redirected-to local mobility anchor, if carried.
     ipv4: 'Optional[IPv4Address]'
+    #: Reserved bits, i.e. the 14 bits after the ``N`` flag.
+    reserved: 'int'
 
     if TYPE_CHECKING:
         def __init__(self, type: 'Enum_Option', length: 'int', ipv6: 'Optional[IPv6Address]',
-                     ipv4: 'Optional[IPv4Address]') -> 'None': ...
+                     ipv4: 'Optional[IPv4Address]', reserved: 'int') -> 'None': ...
 
 
 @info_final
@@ -1693,11 +1735,13 @@ class IPv4TrafficOffloadSelectorOption(Option):
     #: Offload mode flag. Unset offloads the flows matching the selector; set
     #: offloads everything except them.
     mode: 'bool'
+    #: Reserved bits, i.e. the 31 bits after the ``M`` flag.
+    reserved: 'int'
     #: Traffic selector sub-options.
     selector: 'OrderedMultiDict[Enum_FlowIDSuboption, FlowIdentificationSuboption]'
 
     if TYPE_CHECKING:
-        def __init__(self, type: 'Enum_Option', length: 'int', mode: 'bool',
+        def __init__(self, type: 'Enum_Option', length: 'int', mode: 'bool', reserved: 'int',
                      selector: 'OrderedMultiDict[Enum_FlowIDSuboption, FlowIdentificationSuboption]') -> 'None': ...
 
 
@@ -1710,6 +1754,8 @@ class DynamicIPMulticastSelectorOption(Option):
     #: Selector mode flag. Set routes the group locally, unset via the home
     #: network.
     mode: 'bool'
+    #: Reserved bits, i.e. the seven bits after the ``M`` flag.
+    reserved: 'int'
     #: Number of multicast address records carried in :attr:`data`.
     records: 'int'
     #: Multicast address records. These are MLD or IGMP structures belonging to
@@ -1718,7 +1764,7 @@ class DynamicIPMulticastSelectorOption(Option):
     data: 'bytes'
 
     if TYPE_CHECKING:
-        def __init__(self, type: 'Enum_Option', length: 'int', protocol: 'int', mode: 'bool',
+        def __init__(self, type: 'Enum_Option', length: 'int', protocol: 'int', mode: 'bool', reserved: 'int',
                      records: 'int', data: 'bytes') -> 'None': ...
 
 
@@ -1728,13 +1774,15 @@ class DelegatedMNPOption(Option):
 
     #: IPv4 prefix flag, saying which family :attr:`prefix` is in.
     ipv4: 'bool'
+    #: Reserved bits, i.e. the seven bits after the ``V`` flag.
+    reserved: 'int'
     #: Prefix length.
     prefix_length: 'int'
     #: Delegated mobile network prefix, IPv4 or IPv6 as :attr:`ipv4` says.
     prefix: 'IPv4Address | IPv6Address'
 
     if TYPE_CHECKING:
-        def __init__(self, type: 'Enum_Option', length: 'int', ipv4: 'bool',
+        def __init__(self, type: 'Enum_Option', length: 'int', ipv4: 'bool', reserved: 'int',
                      prefix_length: 'int',
                      prefix: 'IPv4Address | IPv6Address') -> 'None': ...
 
@@ -1806,12 +1854,14 @@ class PerSessionBitRateAttribute(QoSAttribute):
     service: 'bool'
     #: Guaranteed-bit-rate exclusion flag.
     exclude: 'bool'
+    #: Reserved bits, i.e. the 14 bits after the ``E`` flag.
+    reserved: 'int'
     #: Bit rate, in **bits** per second.
     rate: 'int'
 
     if TYPE_CHECKING:
         def __init__(self, type: 'Enum_QoSAttribute', length: 'int', service: 'bool',
-                     exclude: 'bool', rate: 'int') -> 'None': ...
+                     exclude: 'bool', reserved: 'int', rate: 'int') -> 'None': ...
 
 
 @info_final
@@ -2011,11 +2061,13 @@ class MAGMultipathBindingOption(Option):
     bulk: 'bool'
     #: Registration overwrite flag.
     overwrite: 'bool'
+    #: Reserved bits, i.e. the 22 bits after the ``O`` flag.
+    reserved: 'int'
 
     if TYPE_CHECKING:
         def __init__(self, type: 'Enum_Option', length: 'int', att: 'Enum_AccessType',
                      label: 'int', bid: 'int', bulk: 'bool',
-                     overwrite: 'bool') -> 'None': ...
+                     overwrite: 'bool', reserved: 'int') -> 'None': ...
 
 
 @info_final
diff --git a/pcapkit/protocols/internet/mh.py b/pcapkit/protocols/internet/mh.py
index 90379becbd..5bf25b0b9a 100644
--- a/pcapkit/protocols/internet/mh.py
+++ b/pcapkit/protocols/internet/mh.py
@@ -2094,6 +2094,7 @@ def _read_msg_fbu(self, schema: 'Schema_FastBindingUpdateMessage', *,
             home=bool(schema.flags['H']),
             lla_compat=bool(schema.flags['L']),
             key_mngt=bool(schema.flags['K']),
+            flags_reserved=schema.flags['reserved'],
             lifetime=datetime.timedelta(seconds=schema.lifetime),
             options=self._read_mh_options(schema.options),
         )
@@ -2149,6 +2150,7 @@ def _read_msg_fback(self, schema: 'Schema_FastBindingAcknowledgmentMessage', *,
             chksum=header.chksum,
             status=FastBindingAcknowledgmentStatus(schema.status),
             key_mngt=bool(schema.flags['K']),
+            flags_reserved=schema.flags['reserved'],
             seq=schema.seq,
             lifetime=datetime.timedelta(seconds=schema.lifetime),
             options=self._read_mh_options(schema.options),
@@ -2286,6 +2288,7 @@ def _read_msg_hi(self, schema: 'Schema_HandoverInitiateMessage', *,
             buffer=bool(schema.flags['U']),
             proxy=bool(schema.flags['P']),
             forward=bool(schema.flags['F']),
+            flags_reserved=schema.flags['reserved'],
             code=schema.code,
             options=self._read_mh_options(schema.options),
         )
@@ -2336,6 +2339,7 @@ def _read_msg_hack(self, schema: 'Schema_HandoverAcknowledgeMessage', *,
             buffer=bool(schema.flags['U']),
             proxy=bool(schema.flags['P']),
             forward=bool(schema.flags['F']),
+            flags_reserved=schema.flags['reserved'],
             code=schema.code,
             options=self._read_mh_options(schema.options),
         )
@@ -2440,6 +2444,7 @@ def _read_msg_hb(self, schema: 'Schema_HeartbeatMessage', *,
             chksum=header.chksum,
             unsolicited=bool(schema.flags['U']),
             response=bool(schema.flags['R']),
+            flags_reserved=schema.flags['reserved'],
             seq=schema.seq,
             options=self._read_mh_options(schema.options),
         )
@@ -2512,6 +2517,7 @@ def _read_msg_brm(self, schema: 'Schema_BindingRevocationMessage', *,
             proxy=bool(schema.flags['P']),
             ipv4_hoa=bool(schema.flags['V']),
             global_revocation=bool(schema.flags['G']),
+            flags_reserved=schema.flags['reserved'],
             options=self._read_mh_options(schema.options),
         )
         return data
@@ -2605,6 +2611,7 @@ def _read_msg_lra(self, schema: 'Schema_LocalizedRoutingAcknowledgmentMessage',
             chksum=header.chksum,
             seq=schema.seq,
             unsolicited=bool(schema.flags['U']),
+            flags_reserved=schema.flags['reserved'],
             status=LocalizedRoutingStatus(schema.status),
             lifetime=datetime.timedelta(seconds=schema.lifetime),
             options=self._read_mh_options(schema.options),
@@ -2653,6 +2660,7 @@ def _read_msg_upn(self, schema: 'Schema_UpdateNotificationMessage', *,
             reason=schema.reason,
             ack=bool(schema.flags['A']),
             retransmit=bool(schema.flags['D']),
+            flags_reserved=schema.flags['reserved'],
             options=self._read_mh_options(schema.options),
         )
         return data
@@ -2759,6 +2767,7 @@ def _read_msg_fbm(self, schema: 'Schema_FlowBindingMessage', *,
             seq=schema.seq,
             code=schema.code,
             ack=bool(schema.flags['A']),
+            flags_reserved=schema.flags['reserved'],
             options=self._read_mh_options(schema.options),
         )
         return data
@@ -2840,6 +2849,7 @@ def _read_msg_sr(self, schema: 'Schema_SubscriptionResponseMessage', *,
             chksum=header.chksum,
             seq=schema.seq,
             info=bool(schema.flags['I']),
+            flags_reserved=schema.flags['reserved'],
             options=self._read_mh_options(schema.options),
         )
         return data
@@ -3740,6 +3750,7 @@ def _read_opt_dns(self, schema: 'Schema_DNSUpdateOption', *,
             length=self._mh_option_length(schema.length),
             status=schema.status,
             remove=bool(schema.flags['R']),
+            reserved=schema.flags['reserved'],
             identity=schema.identity,
         )
         return data
@@ -4210,6 +4221,7 @@ def _read_opt_ipv4_ack(self, schema: 'Schema_IPv4AddressAcknowledgementOption',
             length=self._mh_option_length(schema.length),
             status=schema.status,
             prefix_length=schema.flags['prefix_length'],
+            reserved=schema.flags['reserved'],
             address=schema.address,
         )
         return data
@@ -4251,6 +4263,7 @@ def _read_opt_nat(self, schema: 'Schema_NATDetectionOption', *,
             type=schema.type,
             length=self._mh_option_length(schema.length),
             force=bool(schema.flags['F']),
+            reserved=schema.flags['reserved'],
             refresh=datetime.timedelta(seconds=schema.refresh),
         )
         return data
@@ -4425,6 +4438,7 @@ def _read_opt_ipv4_hoa_req(self, schema: 'Schema_IPv4HomeAddressRequestOption',
             type=schema.type,
             length=self._mh_option_length(schema.length),
             prefix_length=schema.flags['prefix_length'],
+            reserved=schema.flags['reserved'],
             address=schema.address,
         )
         return data
@@ -4467,6 +4481,7 @@ def _read_opt_ipv4_hoa_rep(self, schema: 'Schema_IPv4HomeAddressReplyOption', *,
             length=self._mh_option_length(schema.length),
             status=schema.status,
             prefix_length=schema.flags['prefix_length'],
+            reserved=schema.flags['reserved'],
             address=schema.address,
         )
         return data
@@ -4540,6 +4555,7 @@ def _read_opt_ipv4_dhcp(self, schema: 'Schema_IPv4DHCPSupportModeOption', *,
             type=schema.type,
             length=self._mh_option_length(schema.length),
             mode=Enum_DHCPSupportMode(schema.flags['S']),
+            reserved=schema.flags['reserved'],
         )
         return data
 
@@ -4720,6 +4736,7 @@ def _read_opt_transient(self, schema: 'Schema_TransientBindingOption', *,
             type=schema.type,
             length=self._mh_option_length(schema.length),
             late=bool(schema.flags['L']),
+            reserved=schema.flags['reserved'],
             lifetime=datetime.timedelta(milliseconds=schema.lifetime * 100),
         )
         return data
@@ -5004,6 +5021,7 @@ def _read_opt_redirect(self, schema: 'Schema_RedirectOption', *,
             length=self._mh_option_length(schema.length),
             ipv6=schema.ipv6,
             ipv4=schema.ipv4,
+            reserved=schema.flags['reserved'],
         )
         return data
 
@@ -5382,6 +5400,7 @@ def _read_opt_offload(self, schema: 'Schema_IPv4TrafficOffloadSelectorOption', *
             type=schema.type,
             length=self._mh_option_length(schema.length),
             mode=bool(schema.flags['M']),
+            reserved=schema.flags['reserved'],
             selector=self._read_fid_suboptions(schema.selector),
         )
         return data
@@ -5437,6 +5456,7 @@ def _read_opt_mcast_sel(self, schema: 'Schema_DynamicIPMulticastSelectorOption',
             length=self._mh_option_length(schema.length),
             protocol=schema.protocol,
             mode=bool(schema.flags['M']),
+            reserved=schema.flags['reserved'],
             records=schema.records,
             data=schema.data,
         )
@@ -5489,6 +5509,7 @@ def _read_opt_dmnp(self, schema: 'Schema_DelegatedMNPOption', *,
             type=schema.type,
             length=self._mh_option_length(schema.length),
             ipv4=ipv4,
+            reserved=schema.flags['reserved'],
             prefix_length=schema.prefix_length,
             prefix=schema.prefix,
         )
@@ -5627,6 +5648,7 @@ def _read_qos_attributes(
                     length=self._mh_option_length(session.length),
                     service=bool(session.flags['S']),
                     exclude=bool(session.flags['E']),
+                    reserved=session.flags['reserved'],
                     rate=session.rate,
                 )  # type: Data_QoSAttribute
             elif code in (Enum_QoSAttribute.Per_MN_Agg_Max_DL_Bit_Rate,
@@ -6014,6 +6036,7 @@ def _read_opt_mag_mp(self, schema: 'Schema_MAGMultipathBindingOption', *,
             bid=schema.bid,
             bulk=bulk,
             overwrite=overwrite,
+            reserved=schema.flags['reserved'],
         )
         return data
 
@@ -6468,6 +6491,7 @@ def _read_ext_multiprefix(self, schema: 'Schema_MultiPrefixExtension', *,
             type=schema.type,
             length=self._mh_extension_length(schema.length),
             flag=bool(schema.flags['P']),
+            reserved=schema.flags['reserved'],
             prefixes=tuple(schema.prefixes),
         )
         return data
@@ -6901,6 +6925,7 @@ def _make_msg_fbu(self, message: 'Optional[Data_FastBindingUpdateMessage]' = Non
                       key_mngt: 'bool' = False,
                       lifetime: 'int | timedelta' = 4,  # reasonable default value
                       options: 'Optional[Option | list[Schema_Option | tuple[Enum_Option, dict[str, Any]] | bytes]]' = None,
+                      flags_reserved: 'int' = 0,
                       **kwargs: 'Any') -> 'Schema_FastBindingUpdateMessage':
         """Make MH fast binding update (FBU) message type.
 
@@ -6916,6 +6941,7 @@ def _make_msg_fbu(self, message: 'Optional[Data_FastBindingUpdateMessage]' = Non
                 one counts seconds rather than units of 4 seconds
                 [:rfc:`5568#section-6.2.2`], so the value is not scaled.
             options: Mobility options.
+            flags_reserved: Reserved bits, i.e. the 12 bits after the ``K`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -6928,6 +6954,7 @@ def _make_msg_fbu(self, message: 'Optional[Data_FastBindingUpdateMessage]' = Non
             home = message.home
             lla_compat = message.lla_compat
             key_mngt = message.key_mngt
+            flags_reserved = message.flags_reserved
             lifetime_val = math.ceil(message.lifetime.total_seconds())
             options = message.options
         else:
@@ -6941,6 +6968,7 @@ def _make_msg_fbu(self, message: 'Optional[Data_FastBindingUpdateMessage]' = Non
                 'H': home,
                 'L': lla_compat,
                 'K': key_mngt,
+                'reserved': flags_reserved,
             },
             lifetime=lifetime_val,
             options=self._make_mh_options(options),
@@ -6955,6 +6983,7 @@ def _make_msg_fback(self, message: 'Optional[Data_FastBindingAcknowledgmentMessa
                         seq: 'int' = 0,
                         lifetime: 'int | timedelta' = 4,  # reasonable default value
                         options: 'Optional[Option | list[Schema_Option | tuple[Enum_Option, dict[str, Any]] | bytes]]' = None,
+                        flags_reserved: 'int' = 0,
                         **kwargs: 'Any') -> 'Schema_FastBindingAcknowledgmentMessage':
         """Make MH fast binding acknowledgment (FBack) message type.
 
@@ -6972,6 +7001,7 @@ def _make_msg_fback(self, message: 'Optional[Data_FastBindingAcknowledgmentMessa
                 one counts seconds rather than units of 4 seconds
                 [:rfc:`5568#section-6.2.3`], so the value is not scaled.
             options: Mobility options.
+            flags_reserved: Reserved bits, i.e. the seven bits after the ``K`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -6981,6 +7011,7 @@ def _make_msg_fback(self, message: 'Optional[Data_FastBindingAcknowledgmentMessa
         if message is not None:
             status_val = message.status
             key_mngt = message.key_mngt
+            flags_reserved = message.flags_reserved
             seq = message.seq
             lifetime_val = math.ceil(message.lifetime.total_seconds())
             options = message.options
@@ -6994,6 +7025,7 @@ def _make_msg_fback(self, message: 'Optional[Data_FastBindingAcknowledgmentMessa
             status=status_val,
             flags={
                 'K': key_mngt,
+                'reserved': flags_reserved,
             },
             seq=seq,
             lifetime=lifetime_val,
@@ -7055,6 +7087,7 @@ def _make_msg_hi(self, message: 'Optional[Data_HandoverInitiateMessage]' = None,
                      code_namespace: 'Optional[dict[str, int] | dict[int, str] | Type[StdlibEnum] | Type[AenumEnum]]' = None,  # pylint: disable=line-too-long
                      code_reversed: 'bool' = False,
                      options: 'Optional[Option | list[Schema_Option | tuple[Enum_Option, dict[str, Any]] | bytes]]' = None,
+                     flags_reserved: 'int' = 0,
                      **kwargs: 'Any') -> 'Schema_HandoverInitiateMessage':
         """Make MH handover initiate (HI) message type.
 
@@ -7070,6 +7103,7 @@ def _make_msg_hi(self, message: 'Optional[Data_HandoverInitiateMessage]' = None,
             code_namespace: Code namespace.
             code_reversed: Reverse code namespace.
             options: Mobility options.
+            flags_reserved: Reserved bits, i.e. the four bits after the ``F`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -7082,6 +7116,7 @@ def _make_msg_hi(self, message: 'Optional[Data_HandoverInitiateMessage]' = None,
             buffer = message.buffer
             proxy = message.proxy
             forward = message.forward
+            flags_reserved = message.flags_reserved
             code_val = message.code
             options = message.options
         else:
@@ -7096,6 +7131,7 @@ def _make_msg_hi(self, message: 'Optional[Data_HandoverInitiateMessage]' = None,
                 'U': buffer,
                 'P': proxy,
                 'F': forward,
+                'reserved': flags_reserved,
             },
             code=code_val,
             options=self._make_mh_options(options),
@@ -7111,6 +7147,7 @@ def _make_msg_hack(self, message: 'Optional[Data_HandoverAcknowledgeMessage]' =
                        code_namespace: 'Optional[dict[str, int] | dict[int, str] | Type[StdlibEnum] | Type[AenumEnum]]' = None,  # pylint: disable=line-too-long
                        code_reversed: 'bool' = False,
                        options: 'Optional[Option | list[Schema_Option | tuple[Enum_Option, dict[str, Any]] | bytes]]' = None,
+                       flags_reserved: 'int' = 0,
                        **kwargs: 'Any') -> 'Schema_HandoverAcknowledgeMessage':
         """Make MH handover acknowledge (HAck) message type.
 
@@ -7125,6 +7162,7 @@ def _make_msg_hack(self, message: 'Optional[Data_HandoverAcknowledgeMessage]' =
             code_namespace: Code namespace.
             code_reversed: Reverse code namespace.
             options: Mobility options.
+            flags_reserved: Reserved bits, i.e. the five bits after the ``F`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -7136,6 +7174,7 @@ def _make_msg_hack(self, message: 'Optional[Data_HandoverAcknowledgeMessage]' =
             buffer = message.buffer
             proxy = message.proxy
             forward = message.forward
+            flags_reserved = message.flags_reserved
             code_val = message.code
             options = message.options
         else:
@@ -7149,6 +7188,7 @@ def _make_msg_hack(self, message: 'Optional[Data_HandoverAcknowledgeMessage]' =
                 'U': buffer,
                 'P': proxy,
                 'F': forward,
+                'reserved': flags_reserved,
             },
             code=code_val,
             options=self._make_mh_options(options),
@@ -7189,6 +7229,7 @@ def _make_msg_hb(self, message: 'Optional[Data_HeartbeatMessage]' = None, *,
                      response: 'bool' = False,
                      seq: 'int' = 0,
                      options: 'Optional[Option | list[Schema_Option | tuple[Enum_Option, dict[str, Any]] | bytes]]' = None,
+                     flags_reserved: 'int' = 0,
                      **kwargs: 'Any') -> 'Schema_HeartbeatMessage':
         """Make MH heartbeat message type.
 
@@ -7198,6 +7239,7 @@ def _make_msg_hb(self, message: 'Optional[Data_HeartbeatMessage]' = None, *,
             response: Response flag; unset makes this a heartbeat request.
             seq: Sequence number.
             options: Mobility options.
+            flags_reserved: Reserved bits, i.e. the 14 bits before the ``U`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -7207,6 +7249,7 @@ def _make_msg_hb(self, message: 'Optional[Data_HeartbeatMessage]' = None, *,
         if message is not None:
             unsolicited = message.unsolicited
             response = message.response
+            flags_reserved = message.flags_reserved
             seq = message.seq
             options = message.options
         else:
@@ -7216,6 +7259,7 @@ def _make_msg_hb(self, message: 'Optional[Data_HeartbeatMessage]' = None, *,
             flags={
                 'U': unsolicited,
                 'R': response,
+                'reserved': flags_reserved,
             },
             seq=seq,
             options=self._make_mh_options(options),
@@ -7235,6 +7279,7 @@ def _make_msg_brm(self, message: 'Optional[Data_BindingRevocationMessage]' = Non
                       ipv4_hoa: 'bool' = False,
                       global_revocation: 'bool' = False,
                       options: 'Optional[Option | list[Schema_Option | tuple[Enum_Option, dict[str, Any]] | bytes]]' = None,
+                      flags_reserved: 'int' = 0,
                       **kwargs: 'Any') -> 'Schema_BindingRevocationMessage':
         """Make MH binding revocation (BRM) message type.
 
@@ -7255,6 +7300,7 @@ def _make_msg_brm(self, message: 'Optional[Data_BindingRevocationMessage]' = Non
             ipv4_hoa: IPv4 home address binding only flag.
             global_revocation: Global revocation flag.
             options: Mobility options.
+            flags_reserved: Reserved bits, i.e. the 13 bits after the ``G`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -7268,6 +7314,7 @@ def _make_msg_brm(self, message: 'Optional[Data_BindingRevocationMessage]' = Non
             proxy = message.proxy
             ipv4_hoa = message.ipv4_hoa
             global_revocation = message.global_revocation
+            flags_reserved = message.flags_reserved
             options = message.options
         else:
             br_type_val = self._make_index(br_type, br_type_default, namespace=br_type_namespace,  # type: ignore[assignment]
@@ -7284,6 +7331,7 @@ def _make_msg_brm(self, message: 'Optional[Data_BindingRevocationMessage]' = Non
                 'P': proxy,
                 'V': ipv4_hoa,
                 'G': global_revocation,
+                'reserved': flags_reserved,
             },
             options=self._make_mh_options(options),
         )
@@ -7332,6 +7380,7 @@ def _make_msg_lra(self, message: 'Optional[Data_LocalizedRoutingAcknowledgmentMe
                       status_reversed: 'bool' = False,
                       lifetime: 'int | timedelta' = 0,
                       options: 'Optional[Option | list[Schema_Option | tuple[Enum_Option, dict[str, Any]] | bytes]]' = None,
+                      flags_reserved: 'int' = 0,
                       **kwargs: 'Any') -> 'Schema_LocalizedRoutingAcknowledgmentMessage':
         """Make MH localized routing acknowledgment (LRA) message type.
 
@@ -7347,6 +7396,7 @@ def _make_msg_lra(self, message: 'Optional[Data_LocalizedRoutingAcknowledgmentMe
             lifetime: Lifetime, in seconds or as a
                 :class:`~datetime.timedelta`.
             options: Mobility options.
+            flags_reserved: Reserved bits, i.e. the seven bits after the ``U`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -7356,6 +7406,7 @@ def _make_msg_lra(self, message: 'Optional[Data_LocalizedRoutingAcknowledgmentMe
         if message is not None:
             seq = message.seq
             unsolicited = message.unsolicited
+            flags_reserved = message.flags_reserved
             status_val = message.status  # type: int
             lifetime_val = math.ceil(message.lifetime.total_seconds())
             options = message.options
@@ -7369,6 +7420,7 @@ def _make_msg_lra(self, message: 'Optional[Data_LocalizedRoutingAcknowledgmentMe
             seq=seq,
             flags={
                 'U': unsolicited,
+                'reserved': flags_reserved,
             },
             status=status_val,
             lifetime=lifetime_val,
@@ -7384,6 +7436,7 @@ def _make_msg_upn(self, message: 'Optional[Data_UpdateNotificationMessage]' = No
                       ack: 'bool' = False,
                       retransmit: 'bool' = False,
                       options: 'Optional[Option | list[Schema_Option | tuple[Enum_Option, dict[str, Any]] | bytes]]' = None,
+                      flags_reserved: 'int' = 0,
                       **kwargs: 'Any') -> 'Schema_UpdateNotificationMessage':
         """Make MH update notification (UPN) message type.
 
@@ -7397,6 +7450,7 @@ def _make_msg_upn(self, message: 'Optional[Data_UpdateNotificationMessage]' = No
             ack: Acknowledgement requested flag.
             retransmit: Retransmission flag.
             options: Mobility options.
+            flags_reserved: Reserved bits, i.e. the 14 bits after the ``D`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -7408,6 +7462,7 @@ def _make_msg_upn(self, message: 'Optional[Data_UpdateNotificationMessage]' = No
             reason_val = message.reason  # type: Enum_UpdateNotificationReason
             ack = message.ack
             retransmit = message.retransmit
+            flags_reserved = message.flags_reserved
             options = message.options
         else:
             reason_val = self._make_index(reason, reason_default, namespace=reason_namespace,  # type: ignore[assignment]
@@ -7420,6 +7475,7 @@ def _make_msg_upn(self, message: 'Optional[Data_UpdateNotificationMessage]' = No
             flags={
                 'A': ack,
                 'D': retransmit,
+                'reserved': flags_reserved,
             },
             options=self._make_mh_options(options),
         )
@@ -7475,6 +7531,7 @@ def _make_msg_fbm(self, message: 'Optional[Data_FlowBindingMessage]' = None, *,
                       code_reversed: 'bool' = False,
                       ack: 'bool' = False,
                       options: 'Optional[Option | list[Schema_Option | tuple[Enum_Option, dict[str, Any]] | bytes]]' = None,
+                      flags_reserved: 'int' = 0,
                       **kwargs: 'Any') -> 'Schema_FlowBindingMessage':
         """Make MH flow binding (FB) message type.
 
@@ -7493,6 +7550,7 @@ def _make_msg_fbm(self, message: 'Optional[Data_FlowBindingMessage]' = None, *,
             ack: Acknowledgement requested flag. Meaningful only in an
                 indication.
             options: Mobility options.
+            flags_reserved: Reserved bits, i.e. the seven bits after the ``A`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -7504,6 +7562,7 @@ def _make_msg_fbm(self, message: 'Optional[Data_FlowBindingMessage]' = None, *,
             seq = message.seq
             code_val = message.code  # type: Enum_FlowBindingIndicationTrigger | Enum_FlowBindingACKStatus
             ack = message.ack
+            flags_reserved = message.flags_reserved
             options = message.options
         else:
             fb_type_val = self._make_index(fb_type, fb_type_default, namespace=fb_type_namespace,  # type: ignore[assignment]
@@ -7518,6 +7577,7 @@ def _make_msg_fbm(self, message: 'Optional[Data_FlowBindingMessage]' = None, *,
             code=code_val,
             flags={
                 'A': ack,
+                'reserved': flags_reserved,
             },
             options=self._make_mh_options(options),
         )
@@ -7553,6 +7613,7 @@ def _make_msg_sr(self, message: 'Optional[Data_SubscriptionResponseMessage]' = N
                      seq: 'int' = 0,
                      info: 'bool' = False,
                      options: 'Optional[Option | list[Schema_Option | tuple[Enum_Option, dict[str, Any]] | bytes]]' = None,
+                     flags_reserved: 'int' = 0,
                      **kwargs: 'Any') -> 'Schema_SubscriptionResponseMessage':
         """Make MH subscription response (SR) message type.
 
@@ -7561,6 +7622,7 @@ def _make_msg_sr(self, message: 'Optional[Data_SubscriptionResponseMessage]' = N
             seq: Sequence number, echoed from the query.
             info: Multicast information flag.
             options: Mobility options.
+            flags_reserved: Reserved bits, i.e. the seven bits after the ``I`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -7570,6 +7632,7 @@ def _make_msg_sr(self, message: 'Optional[Data_SubscriptionResponseMessage]' = N
         if message is not None:
             seq = message.seq
             info = message.info
+            flags_reserved = message.flags_reserved
             options = message.options
         else:
             options = options or []
@@ -7578,6 +7641,7 @@ def _make_msg_sr(self, message: 'Optional[Data_SubscriptionResponseMessage]' = N
             seq=seq,
             flags={
                 'I': info,
+                'reserved': flags_reserved,
             },
             options=self._make_mh_options(options),
         )
@@ -8547,6 +8611,7 @@ def _make_opt_dns(self, type: 'Enum_Option', option: 'Optional[Data_DNSUpdateOpt
                       status_reversed: 'bool' = False,
                       remove: 'bool' = False,
                       identity: 'bytes' = b'',
+                      reserved: 'int' = 0,
                       **kwargs: 'Any') -> 'Schema_DNSUpdateOption':
         """Make MH DNS-UPDATE-TYPE option.
 
@@ -8559,6 +8624,7 @@ def _make_opt_dns(self, type: 'Enum_Option', option: 'Optional[Data_DNSUpdateOpt
             status_reversed: Reverse status namespace.
             remove: Remove flag.
             identity: Mobile node identity, in FQDN form.
+            reserved: Reserved bits, i.e. the seven bits after the ``R`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -8568,6 +8634,7 @@ def _make_opt_dns(self, type: 'Enum_Option', option: 'Optional[Data_DNSUpdateOpt
         if option is not None:
             status_val = option.status  # type: Enum_DNSStatusCode
             remove = option.remove
+            reserved = option.reserved
             identity = option.identity
         else:
             status_val = self._make_index(status, status_default, namespace=status_namespace,  # type: ignore[assignment]
@@ -8577,7 +8644,7 @@ def _make_opt_dns(self, type: 'Enum_Option', option: 'Optional[Data_DNSUpdateOpt
             type=type,
             length=2 + len(identity),
             status=status_val,
-            flags={'R': int(remove)},
+            flags={'R': int(remove), 'reserved': reserved},
             identity=identity,
         )
 
@@ -8906,6 +8973,7 @@ def _make_opt_ipv4_ack(self, type: 'Enum_Option',
                            status_reversed: 'bool' = False,
                            prefix_length: 'int' = 32,
                            address: 'bytes | str | int | IPv4Address' = '0.0.0.0',
+                           reserved: 'int' = 0,
                            **kwargs: 'Any') -> 'Schema_IPv4AddressAcknowledgementOption':
         """Make MH IPv4 address acknowledgement option.
 
@@ -8918,6 +8986,7 @@ def _make_opt_ipv4_ack(self, type: 'Enum_Option',
             status_reversed: Reverse status namespace.
             prefix_length: Allocated prefix length.
             address: Assigned IPv4 home address.
+            reserved: Reserved bits, i.e. the two bits after the prefix length.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -8927,6 +8996,7 @@ def _make_opt_ipv4_ack(self, type: 'Enum_Option',
         if option is not None:
             status_val = option.status  # type: Enum_DSMIPv6HomeAddress
             prefix_length = option.prefix_length
+            reserved = option.reserved
             address = option.address
         else:
             status_val = self._make_index(status, status_default, namespace=status_namespace,  # type: ignore[assignment]
@@ -8939,13 +9009,14 @@ def _make_opt_ipv4_ack(self, type: 'Enum_Option',
             type=type,
             length=6,
             status=status_val,
-            flags={'prefix_length': prefix_length},
+            flags={'prefix_length': prefix_length, 'reserved': reserved},
             address=address,
         )
 
     def _make_opt_nat(self, type: 'Enum_Option', option: 'Optional[Data_NATDetectionOption]' = None, *,
                       force: 'bool' = False,
                       refresh: 'int | timedelta' = 0,
+                      reserved: 'int' = 0,
                       **kwargs: 'Any') -> 'Schema_NATDetectionOption':
         """Make MH NAT detection option.
 
@@ -8955,6 +9026,7 @@ def _make_opt_nat(self, type: 'Enum_Option', option: 'Optional[Data_NATDetection
             force: Force UDP encapsulation flag.
             refresh: Suggested NAT binding refresh interval, in seconds or as a
                 :class:`~datetime.timedelta`.
+            reserved: Reserved bits, i.e. the 15 bits after the ``F`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -8963,6 +9035,7 @@ def _make_opt_nat(self, type: 'Enum_Option', option: 'Optional[Data_NATDetection
         """
         if option is not None:
             force = option.force
+            reserved = option.reserved
             refresh_val = math.ceil(option.refresh.total_seconds())
         else:
             refresh_val = refresh if isinstance(refresh, int) else math.ceil(refresh.total_seconds())
@@ -8970,7 +9043,7 @@ def _make_opt_nat(self, type: 'Enum_Option', option: 'Optional[Data_NATDetection
         return Schema_NATDetectionOption(
             type=type,
             length=6,
-            flags={'F': int(force)},
+            flags={'F': int(force), 'reserved': reserved},
             refresh=refresh_val,
         )
 
@@ -9102,6 +9175,7 @@ def _make_opt_ipv4_hoa_req(self, type: 'Enum_Option',
                                                           option: 'Optional[Data_IPv4HomeAddressRequestOption]' = None, *,
                                prefix_length: 'int' = 32,
                                address: 'bytes | str | int | IPv4Address' = '0.0.0.0',
+                               reserved: 'int' = 0,
                                **kwargs: 'Any') -> 'Schema_IPv4HomeAddressRequestOption':
         """Make MH IPv4 home address request option.
 
@@ -9110,6 +9184,7 @@ def _make_opt_ipv4_hoa_req(self, type: 'Enum_Option',
             option: Option data model.
             prefix_length: Prefix length of the requested home network.
             address: Requested IPv4 home address.
+            reserved: Reserved bits, i.e. the ten bits after the prefix length.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -9118,6 +9193,7 @@ def _make_opt_ipv4_hoa_req(self, type: 'Enum_Option',
         """
         if option is not None:
             prefix_length = option.prefix_length
+            reserved = option.reserved
             address = option.address
 
         if prefix_length > 32:
@@ -9126,7 +9202,7 @@ def _make_opt_ipv4_hoa_req(self, type: 'Enum_Option',
         return Schema_IPv4HomeAddressRequestOption(
             type=type,
             length=6,
-            flags={'prefix_length': prefix_length},
+            flags={'prefix_length': prefix_length, 'reserved': reserved},
             address=address,
         )
 
@@ -9137,6 +9213,7 @@ def _make_opt_ipv4_hoa_rep(self, type: 'Enum_Option', option: 'Optional[Data_IPv
                                status_reversed: 'bool' = False,
                                prefix_length: 'int' = 32,
                                address: 'bytes | str | int | IPv4Address' = '0.0.0.0',
+                               reserved: 'int' = 0,
                                **kwargs: 'Any') -> 'Schema_IPv4HomeAddressReplyOption':
         """Make MH IPv4 home address reply option.
 
@@ -9149,6 +9226,7 @@ def _make_opt_ipv4_hoa_rep(self, type: 'Enum_Option', option: 'Optional[Data_IPv
             status_reversed: Reverse status namespace.
             prefix_length: Prefix length of the assigned home network.
             address: Assigned IPv4 home address.
+            reserved: Reserved bits, i.e. the two bits after the prefix length.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -9158,6 +9236,7 @@ def _make_opt_ipv4_hoa_rep(self, type: 'Enum_Option', option: 'Optional[Data_IPv
         if option is not None:
             status_val = option.status  # type: Enum_HomeAddressReply
             prefix_length = option.prefix_length
+            reserved = option.reserved
             address = option.address
         else:
             status_val = self._make_index(status, status_default, namespace=status_namespace,  # type: ignore[assignment]
@@ -9170,7 +9249,7 @@ def _make_opt_ipv4_hoa_rep(self, type: 'Enum_Option', option: 'Optional[Data_IPv
             type=type,
             length=6,
             status=status_val,
-            flags={'prefix_length': prefix_length},
+            flags={'prefix_length': prefix_length, 'reserved': reserved},
             address=address,
         )
 
@@ -9204,6 +9283,7 @@ def _make_opt_ipv4_dhcp(self, type: 'Enum_Option', option: 'Optional[Data_IPv4DH
                             mode_default: 'Optional[int]' = None,
                             mode_namespace: 'Optional[dict[str, int] | dict[int, str] | Type[StdlibEnum] | Type[AenumEnum]]' = None,  # pylint: disable=line-too-long
                             mode_reversed: 'bool' = False,
+                            reserved: 'int' = 0,
                             **kwargs: 'Any') -> 'Schema_IPv4DHCPSupportModeOption':
         """Make MH IPv4 DHCP support mode option.
 
@@ -9214,6 +9294,7 @@ def _make_opt_ipv4_dhcp(self, type: 'Enum_Option', option: 'Optional[Data_IPv4DH
             mode_default: Default DHCP support mode.
             mode_namespace: DHCP support mode namespace.
             mode_reversed: Reverse DHCP support mode namespace.
+            reserved: Reserved bits, i.e. the 15 bits before the ``S`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -9222,6 +9303,7 @@ def _make_opt_ipv4_dhcp(self, type: 'Enum_Option', option: 'Optional[Data_IPv4DH
         """
         if option is not None:
             mode_val = int(option.mode)
+            reserved = option.reserved
         else:
             mode_val = self._make_index(mode, mode_default, namespace=mode_namespace,
                                         reversed=mode_reversed, pack=False)
@@ -9232,7 +9314,7 @@ def _make_opt_ipv4_dhcp(self, type: 'Enum_Option', option: 'Optional[Data_IPv4DH
         return Schema_IPv4DHCPSupportModeOption(
             type=type,
             length=2,
-            flags={'S': mode_val},
+            flags={'S': mode_val, 'reserved': reserved},
         )
 
     def _make_opt_cr(self, type: 'Enum_Option', option: 'Optional[Data_ContextRequestOption]' = None, *,
@@ -9365,6 +9447,7 @@ def _make_opt_mn_lla_iid(self, type: 'Enum_Option', option: 'Optional[Data_MNLLA
     def _make_opt_transient(self, type: 'Enum_Option', option: 'Optional[Data_TransientBindingOption]' = None, *,
                             late: 'bool' = False,
                             lifetime: 'int | timedelta' = 0,
+                            reserved: 'int' = 0,
                             **kwargs: 'Any') -> 'Schema_TransientBindingOption':
         """Make MH transient binding option.
 
@@ -9374,6 +9457,7 @@ def _make_opt_transient(self, type: 'Enum_Option', option: 'Optional[Data_Transi
             late: Late path switch flag.
             lifetime: Maximum lifetime of the transient state, in units of 100
                 milliseconds or as a :class:`~datetime.timedelta`.
+            reserved: Reserved bits, i.e. the seven bits before the ``L`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -9382,6 +9466,7 @@ def _make_opt_transient(self, type: 'Enum_Option', option: 'Optional[Data_Transi
         """
         if option is not None:
             late = option.late
+            reserved = option.reserved
             lifetime_val = math.ceil(option.lifetime.total_seconds() * 10)
         else:
             lifetime_val = lifetime if isinstance(lifetime, int) else math.ceil(
@@ -9393,7 +9478,7 @@ def _make_opt_transient(self, type: 'Enum_Option', option: 'Optional[Data_Transi
         return Schema_TransientBindingOption(
             type=type,
             length=2,
-            flags={'L': int(late)},
+            flags={'L': int(late), 'reserved': reserved},
             lifetime=lifetime_val,
         )
 
@@ -9609,6 +9694,7 @@ def _make_opt_rc(self, type: 'Enum_Option', option: 'Optional[Data_RedirectCapab
     def _make_opt_redirect(self, type: 'Enum_Option', option: 'Optional[Data_RedirectOption]' = None, *,
                            ipv6: 'Optional[bytes | str | int | IPv6Address]' = None,
                            ipv4: 'Optional[bytes | str | int | IPv4Address]' = None,
+                           reserved: 'int' = 0,
                            **kwargs: 'Any') -> 'Schema_RedirectOption':
         """Make MH redirect mobility option.
 
@@ -9617,6 +9703,7 @@ def _make_opt_redirect(self, type: 'Enum_Option', option: 'Optional[Data_Redirec
             option: Option data model.
             ipv6: IPv6 address of the redirected-to local mobility anchor.
             ipv4: IPv4 address of the redirected-to local mobility anchor.
+            reserved: Reserved bits, i.e. the 14 bits after the ``N`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -9630,6 +9717,7 @@ def _make_opt_redirect(self, type: 'Enum_Option', option: 'Optional[Data_Redirec
         if option is not None:
             ipv6 = option.ipv6
             ipv4 = option.ipv4
+            reserved = option.reserved
 
         if (ipv6 is None) == (ipv4 is None):
             raise ProtocolError(f'{self.alias}: [OptNo {type}] exactly one of the IPv6 and '
@@ -9641,6 +9729,7 @@ def _make_opt_redirect(self, type: 'Enum_Option', option: 'Optional[Data_Redirec
             flags={
                 'K': int(ipv6 is not None),
                 'N': int(ipv4 is not None),
+                'reserved': reserved,
             },
             ipv6=ipv6,
             ipv4=ipv4,
@@ -9940,6 +10029,7 @@ def _make_opt_offload(self, type: 'Enum_Option',
                                                      option: 'Optional[Data_IPv4TrafficOffloadSelectorOption]' = None, *,
                           mode: 'bool' = False,
                           selector: 'Optional[FlowIDSuboption | list[Schema_FlowIdentificationSuboption | tuple[Enum_FlowIDSuboption, dict[str, Any]] | bytes]]' = None,
+                          reserved: 'int' = 0,
                           **kwargs: 'Any') -> 'Schema_IPv4TrafficOffloadSelectorOption':
         """Make MH IPv4 traffic offload selector option.
 
@@ -9948,6 +10038,7 @@ def _make_opt_offload(self, type: 'Enum_Option',
             option: Option data model.
             mode: Offload mode flag.
             selector: Traffic selector sub-options.
+            reserved: Reserved bits, i.e. the 31 bits after the ``M`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -9956,6 +10047,7 @@ def _make_opt_offload(self, type: 'Enum_Option',
         """
         if option is not None:
             mode = option.mode
+            reserved = option.reserved
             selector = option.selector
         else:
             selector = selector or []
@@ -9967,7 +10059,7 @@ def _make_opt_offload(self, type: 'Enum_Option',
         return Schema_IPv4TrafficOffloadSelectorOption(
             type=type,
             length=length,
-            flags={'M': int(mode)},
+            flags={'M': int(mode), 'reserved': reserved},
             selector=entries,
         )
 
@@ -9977,6 +10069,7 @@ def _make_opt_mcast_sel(self, type: 'Enum_Option',
                             mode: 'bool' = False,
                             records: 'int' = 0,
                             data: 'bytes' = b'',
+                            reserved: 'int' = 0,
                             **kwargs: 'Any') -> 'Schema_DynamicIPMulticastSelectorOption':
         """Make MH dynamic IP multicast selector option.
 
@@ -9987,6 +10080,7 @@ def _make_opt_mcast_sel(self, type: 'Enum_Option',
             mode: Selector mode flag.
             records: Number of multicast address records in ``data``.
             data: Multicast address records, opaque to this module.
+            reserved: Reserved bits, i.e. the seven bits after the ``M`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -9996,6 +10090,7 @@ def _make_opt_mcast_sel(self, type: 'Enum_Option',
         if option is not None:
             protocol = option.protocol
             mode = option.mode
+            reserved = option.reserved
             records = option.records
             data = option.data
 
@@ -10003,7 +10098,7 @@ def _make_opt_mcast_sel(self, type: 'Enum_Option',
             type=type,
             length=4 + len(data),
             protocol=protocol,
-            flags={'M': int(mode)},
+            flags={'M': int(mode), 'reserved': reserved},
             records=records,
             data=data,
         )
@@ -10011,6 +10106,7 @@ def _make_opt_mcast_sel(self, type: 'Enum_Option',
     def _make_opt_dmnp(self, type: 'Enum_Option', option: 'Optional[Data_DelegatedMNPOption]' = None, *,
                        prefix_length: 'int' = 64,
                        prefix: 'bytes | str | int | IPv4Address | IPv6Address' = '::',
+                       reserved: 'int' = 0,
                        **kwargs: 'Any') -> 'Schema_DelegatedMNPOption':
         """Make MH delegated mobile network prefix option.
 
@@ -10019,6 +10115,7 @@ def _make_opt_dmnp(self, type: 'Enum_Option', option: 'Optional[Data_DelegatedMN
             option: Option data model.
             prefix_length: Prefix length.
             prefix: Delegated mobile network prefix.
+            reserved: Reserved bits, i.e. the seven bits after the ``V`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -10031,6 +10128,7 @@ def _make_opt_dmnp(self, type: 'Enum_Option', option: 'Optional[Data_DelegatedMN
 
         """
         if option is not None:
+            reserved = option.reserved
             prefix_length = option.prefix_length
             prefix = option.prefix
 
@@ -10050,7 +10148,7 @@ def _make_opt_dmnp(self, type: 'Enum_Option', option: 'Optional[Data_DelegatedMN
         return Schema_DelegatedMNPOption(
             type=type,
             length=6 if ipv4 else 18,
-            flags={'V': int(ipv4)},
+            flags={'V': int(ipv4), 'reserved': reserved},
             prefix_length=prefix_length,
             prefix=addr,
         )
@@ -10172,13 +10270,15 @@ def _make_qos_attribute(self, code: 'Enum_QoSAttribute',
             if option is not None:
                 session = cast('Data_PerSessionBitRateAttribute', option)
                 service, exclude, rate = session.service, session.exclude, session.rate
+                reserved = session.reserved
             else:
                 service = cast('bool', kwargs.get('service', False))
                 exclude = cast('bool', kwargs.get('exclude', False))
+                reserved = cast('int', kwargs.get('reserved', 0))
                 rate = cast('int', kwargs.get('rate', 0))
             return Schema_PerSessionBitRateAttribute(
                 type=code, length=6,
-                flags={'S': int(service), 'E': int(exclude)}, rate=rate)
+                flags={'S': int(service), 'E': int(exclude), 'reserved': reserved}, rate=rate)
 
         if code in (Enum_QoSAttribute.Per_MN_Agg_Max_DL_Bit_Rate,
                     Enum_QoSAttribute.Per_MN_Agg_Max_UL_Bit_Rate,
@@ -10543,6 +10643,7 @@ def _make_opt_mag_mp(self, type: 'Enum_Option', option: 'Optional[Data_MAGMultip
                          bid: 'int' = 1,
                          bulk: 'bool' = False,
                          overwrite: 'bool' = False,
+                         reserved: 'int' = 0,
                          **kwargs: 'Any') -> 'Schema_MAGMultipathBindingOption':
         """Make MH MAG multipath binding option.
 
@@ -10557,6 +10658,7 @@ def _make_opt_mag_mp(self, type: 'Enum_Option', option: 'Optional[Data_MAGMultip
             bid: Binding identifier; ``0`` and ``255`` are reserved.
             bulk: Bulk re-registration flag.
             overwrite: Registration overwrite flag.
+            reserved: Reserved bits, i.e. the 22 bits after the ``O`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -10573,6 +10675,7 @@ def _make_opt_mag_mp(self, type: 'Enum_Option', option: 'Optional[Data_MAGMultip
             bid = option.bid
             bulk = option.bulk
             overwrite = option.overwrite
+            reserved = option.reserved
         else:
             att_val = self._make_index(att, att_default, namespace=att_namespace,  # type: ignore[assignment]
                                        reversed=att_reversed, pack=False)
@@ -10590,6 +10693,7 @@ def _make_opt_mag_mp(self, type: 'Enum_Option', option: 'Optional[Data_MAGMultip
             flags={
                 'B': int(bulk),
                 'O': int(overwrite),
+                'reserved': reserved,
             },
         )
 
@@ -10882,6 +10986,7 @@ def _make_ext_none(self, type: 'Enum_CGAExtension', option: 'Optional[Data_Unkno
     def _make_ext_multiprefix(self, type: 'Enum_CGAExtension', option: 'Optional[Data_MultiPrefixExtension]' = None, *,
                               flag: 'bool' = False,
                               prefixes: 'Optional[list[int]]' = None,
+                              reserved: 'int' = 0,
                               **kwargs: 'Any') -> 'Schema_MultiPrefixExtension':
         """Make CGA multi-prefix extension.
 
@@ -10890,6 +10995,7 @@ def _make_ext_multiprefix(self, type: 'Enum_CGAExtension', option: 'Optional[Dat
             option: Extension data model.
             flag: Public key flag.
             prefixes: Prefixes.
+            reserved: Reserved bits, i.e. the 31 bits after the ``P`` flag.
             **kwargs: Arbitrary keyword arguments.
 
         Returns:
@@ -10898,6 +11004,7 @@ def _make_ext_multiprefix(self, type: 'Enum_CGAExtension', option: 'Optional[Dat
         """
         if option is not None:
             flag = option.flag
+            reserved = option.reserved
             # NOTE: ``list()`` rather than a cast: the data model stores the
             # prefixes as a :obj:`tuple`, which
             # :class:`~pcapkit.corekit.fields.collections.ListField` refuses to
@@ -10919,6 +11026,7 @@ def _make_ext_multiprefix(self, type: 'Enum_CGAExtension', option: 'Optional[Dat
             length=4 + len(prefixes) * 8,
             flags={
                 'P': int(flag),
+                'reserved': reserved,
             },
             prefixes=prefixes,
         )
diff --git a/pcapkit/protocols/schema/internet/mh.py b/pcapkit/protocols/schema/internet/mh.py
index 80cf3664a2..a2a2fd3482 100644
--- a/pcapkit/protocols/schema/internet/mh.py
+++ b/pcapkit/protocols/schema/internet/mh.py
@@ -148,6 +148,7 @@ class MultiPrefixExtensionFlags(TypedDict):
         """Flags for :attr:`MultiPrefixExtension.flags`."""
 
         P: int
+        reserved: int
 
     class BindingUpdateMessageFlags(TypedDict):
         """Flags for :attr:`BindingUpdateMessage.flags`."""
@@ -185,11 +186,13 @@ class FastBindingUpdateMessageFlags(TypedDict):
         H: 'int'
         L: 'int'
         K: 'int'
+        reserved: 'int'
 
     class FastBindingAcknowledgmentMessageFlags(TypedDict):
         """Flags for :attr:`FastBindingAcknowledgmentMessage.flags`."""
 
         K: 'int'
+        reserved: 'int'
 
     class HandoverInitiateMessageFlags(TypedDict):
         """Flags for :attr:`HandoverInitiateMessage.flags`."""
@@ -198,6 +201,7 @@ class HandoverInitiateMessageFlags(TypedDict):
         U: 'int'
         P: 'int'
         F: 'int'
+        reserved: 'int'
 
     class HandoverAcknowledgeMessageFlags(TypedDict):
         """Flags for :attr:`HandoverAcknowledgeMessage.flags`."""
@@ -205,12 +209,14 @@ class HandoverAcknowledgeMessageFlags(TypedDict):
         U: 'int'
         P: 'int'
         F: 'int'
+        reserved: 'int'
 
     class HeartbeatMessageFlags(TypedDict):
         """Flags for :attr:`HeartbeatMessage.flags`."""
 
         U: 'int'
         R: 'int'
+        reserved: 'int'
 
     class FixedPointTimestamp(TypedDict):
         """Fixed-point timestamp of :attr:`TimestampOption.timestamp`."""
@@ -224,32 +230,38 @@ class BindingRevocationMessageFlags(TypedDict):
         P: 'int'
         V: 'int'
         G: 'int'
+        reserved: 'int'
 
     class LocalizedRoutingAcknowledgmentMessageFlags(TypedDict):
         """Flags for :attr:`LocalizedRoutingAcknowledgmentMessage.flags`."""
 
         U: 'int'
+        reserved: 'int'
 
     class FlowBindingMessageFlags(TypedDict):
         """Flags for :attr:`FlowBindingMessage.flags`."""
 
         A: 'int'
+        reserved: 'int'
 
     class UpdateNotificationMessageFlags(TypedDict):
         """Flags for :attr:`UpdateNotificationMessage.flags`."""
 
         A: 'int'
         D: 'int'
+        reserved: 'int'
 
     class SubscriptionResponseMessageFlags(TypedDict):
         """Flags for :attr:`SubscriptionResponseMessage.flags`."""
 
         I: 'int'
+        reserved: 'int'
 
     class DNSUpdateOptionFlags(TypedDict):
         """Flags for :attr:`DNSUpdateOption.flags`."""
 
         R: 'int'
+        reserved: 'int'
 
     class IPv4HomeAddressOptionFlags(TypedDict):
         """Prefix length and flags of :attr:`IPv4HomeAddressOption.flags`."""
@@ -265,22 +277,26 @@ class PrefixLengthOnly(TypedDict):
         :attr:`IPv4HomeAddressReplyOption.flags`."""
 
         prefix_length: 'int'
+        reserved: 'int'
 
     class NATDetectionOptionFlags(TypedDict):
         """Flags for :attr:`NATDetectionOption.flags`."""
 
         F: 'int'
+        reserved: 'int'
 
     class IPv4DHCPSupportModeOptionFlags(TypedDict):
         """Flags for :attr:`IPv4DHCPSupportModeOption.flags`."""
 
         S: 'int'
+        reserved: 'int'
 
     class RedirectOptionFlags(TypedDict):
         """Flags for :attr:`RedirectOption.flags`."""
 
         K: 'int'
         N: 'int'
+        reserved: 'int'
 
     class BindingIdentifierOptionFlags(TypedDict):
         """Flag and priority of :attr:`BindingIdentifierOption.flags`."""
@@ -292,6 +308,7 @@ class TransientBindingOptionFlags(TypedDict):
         """Flags for :attr:`TransientBindingOption.flags`."""
 
         L: 'int'
+        reserved: 'int'
 
     class ModeFlagOnly(TypedDict):
         """A lone ``M`` mode flag, as in
@@ -299,17 +316,20 @@ class ModeFlagOnly(TypedDict):
         :attr:`IPv4TrafficOffloadSelectorOption.flags`."""
 
         M: 'int'
+        reserved: 'int'
 
     class DelegatedMNPOptionFlags(TypedDict):
         """Flags for :attr:`DelegatedMNPOption.flags`."""
 
         V: 'int'
+        reserved: 'int'
 
     class MAGMultipathBindingOptionFlags(TypedDict):
         """Flags for :attr:`MAGMultipathBindingOption.flags`."""
 
         B: 'int'
         O: 'int'
+        reserved: 'int'
 
     class ANINetworkIdentifierFlags(TypedDict):
         """Flags for :attr:`ANINetworkIdentifierSuboption.flags`."""
@@ -328,6 +348,7 @@ class SessionBitRateFlags(TypedDict):
 
         S: 'int'
         E: 'int'
+        reserved: 'int'
 
     class AllocationRetentionPriorityFields(TypedDict):
         """Priority fields of :attr:`AllocationRetentionPriorityAttribute.priority`."""
@@ -850,6 +871,7 @@ class MultiPrefixExtension(CGAExtension, code=Enum_CGAExtension.Multi_Prefix):
     #: Flags.
     flags: 'MultiPrefixExtensionFlags' = BitField(length=4, namespace={
         'P': (0, 1),
+        'reserved': (1, 31),
     })
     #: Prefixes.
     prefixes: 'list[int]' = ListField(
@@ -1046,6 +1068,7 @@ class DNSUpdateOption(Option, code=Enum_Option.DNS_UPDATE_TYPE):
     #: Flags.
     flags: 'DNSUpdateOptionFlags' = BitField(length=1, namespace={
         'R': (0, 1),
+        'reserved': (1, 7),
     })
     #: Mobile node identity, in FQDN form.
     identity: 'bytes' = BytesField(length=lambda pkt: pkt['length'] - 2)
@@ -1217,6 +1240,7 @@ class IPv4AddressAcknowledgementOption(Option, code=Enum_Option.IPv4_Address_Ack
     #: Prefix length, with 2 reserved bits below it.
     flags: 'PrefixLengthOnly' = BitField(length=1, namespace={
         'prefix_length': (0, 6),
+        'reserved': (6, 2),
     })
     #: IPv4 home address.
     address: 'IPv4Address' = IPv4AddressField()
@@ -1234,6 +1258,7 @@ class NATDetectionOption(Option, code=Enum_Option.NAT_Detection):
     #: Flags.
     flags: 'NATDetectionOptionFlags' = BitField(length=2, namespace={
         'F': (0, 1),
+        'reserved': (1, 15),
     })
     #: Suggested NAT binding refresh time, in seconds.
     refresh: 'int' = UInt32Field()
@@ -1326,6 +1351,7 @@ class IPv4HomeAddressRequestOption(Option, code=Enum_Option.IPv4_Home_Address_Re
     #: Prefix length, with 10 reserved bits below it.
     flags: 'PrefixLengthOnly' = BitField(length=2, namespace={
         'prefix_length': (0, 6),
+        'reserved': (6, 10),
     })
     #: Requested IPv4 home address.
     address: 'IPv4Address' = IPv4AddressField()
@@ -1344,6 +1370,7 @@ class IPv4HomeAddressReplyOption(Option, code=Enum_Option.IPv4_Home_Address_Repl
     #: Prefix length, with 2 reserved bits below it.
     flags: 'PrefixLengthOnly' = BitField(length=1, namespace={
         'prefix_length': (0, 6),
+        'reserved': (6, 2),
     })
     #: Assigned IPv4 home address.
     address: 'IPv4Address' = IPv4AddressField()
@@ -1375,6 +1402,7 @@ class IPv4DHCPSupportModeOption(Option, code=Enum_Option.IPv4_DHCP_Support_Mode)
     #: Flags. The ``S`` bit is the **last** bit of the option, not the first
     #: [:rfc:`5844#section-3.3.4`].
     flags: 'IPv4DHCPSupportModeOptionFlags' = BitField(length=2, namespace={
+        'reserved': (0, 15),
         'S': (15, 1),
     })
 
@@ -1462,6 +1490,7 @@ class TransientBindingOption(Option, code=Enum_Option.Transient_Binding):
 
     #: Flags.
     flags: 'TransientBindingOptionFlags' = BitField(length=1, namespace={
+        'reserved': (0, 7),
         'L': (7, 1),
     })
     #: Maximum lifetime of the transient state, in units of 100 milliseconds.
@@ -1679,6 +1708,7 @@ class RedirectOption(Option, code=Enum_Option.Redirect_Mobility_Option):
     flags: 'RedirectOptionFlags' = BitField(length=2, namespace={
         'K': (0, 1),
         'N': (1, 1),
+        'reserved': (2, 14),
     })
     #: IPv6 address of the redirected-to LMA, present when ``K`` is set.
     ipv6: 'Optional[IPv6Address]' = ConditionalField(
@@ -1934,6 +1964,7 @@ class IPv4TrafficOffloadSelectorOption(Option, code=Enum_Option.IPv4_Traffic_Off
     #: Flags.
     flags: 'ModeFlagOnly' = BitField(length=4, namespace={
         'M': (0, 1),
+        'reserved': (1, 31),
     })
     #: Traffic selector, carried as the traffic selector sub-option of
     #: :rfc:`6089#section-4.2.1.4`. Optional in a proxy binding update and
@@ -1970,6 +2001,7 @@ class DynamicIPMulticastSelectorOption(Option, code=Enum_Option.Dynamic_IP_Multi
     #: Flags.
     flags: 'ModeFlagOnly' = BitField(length=1, namespace={
         'M': (0, 1),
+        'reserved': (1, 7),
     })
     #: Number of multicast address records.
     records: 'int' = UInt16Field()
@@ -1988,6 +2020,7 @@ class DelegatedMNPOption(Option, code=Enum_Option.Delegated_Mobile_Network_Prefi
     #: Flags.
     flags: 'DelegatedMNPOptionFlags' = BitField(length=1, namespace={
         'V': (0, 1),
+        'reserved': (1, 7),
     })
     #: Prefix length.
     prefix_length: 'int' = UInt8Field()
@@ -2111,6 +2144,7 @@ class PerSessionBitRateAttribute(
     flags: 'SessionBitRateFlags' = BitField(length=2, namespace={
         'S': (0, 1),
         'E': (1, 1),
+        'reserved': (2, 14),
     })
     #: Bit rate, in bits per second.
     rate: 'int' = UInt32Field()
@@ -2378,6 +2412,7 @@ class MAGMultipathBindingOption(Option, code=Enum_Option.MAG_Multipath_Binding):
     flags: 'MAGMultipathBindingOptionFlags' = BitField(length=3, namespace={
         'B': (0, 1),
         'O': (1, 1),
+        'reserved': (2, 22),
     })
 
     if TYPE_CHECKING:
@@ -2731,6 +2766,7 @@ class FastBindingUpdateMessage(Packet, code=Enum_Packet.Fast_Binding_Update):
         'H': (1, 1),
         'L': (2, 1),
         'K': (3, 1),
+        'reserved': (4, 12),
     })
     #: Lifetime, in seconds [:rfc:`5568#section-6.2.2`].
     lifetime: 'int' = UInt16Field()
@@ -2771,6 +2807,7 @@ class FastBindingAcknowledgmentMessage(Packet, code=Enum_Packet.Fast_Binding_Ack
     #: Flags.
     flags: 'FastBindingAcknowledgmentMessageFlags' = BitField(length=1, namespace={
         'K': (0, 1),
+        'reserved': (1, 7),
     })
     #: Sequence number.
     seq: 'int' = UInt16Field()
@@ -2832,6 +2869,7 @@ class HandoverInitiateMessage(Packet, code=Enum_Packet.Handover_Initiate_Message
         'U': (1, 1),
         'P': (2, 1),
         'F': (3, 1),
+        'reserved': (4, 4),
     })
     #: Code.
     code: 'Enum_HandoverInitiateStatus' = EnumField(length=1, namespace=Enum_HandoverInitiateStatus)
@@ -2860,6 +2898,7 @@ class HandoverAcknowledgeMessage(Packet, code=Enum_Packet.Handover_Acknowledge_M
         'U': (0, 1),
         'P': (1, 1),
         'F': (2, 1),
+        'reserved': (3, 5),
     })
     #: Code.
     code: 'Enum_HandoverACKStatus' = EnumField(length=1, namespace=Enum_HandoverACKStatus)
@@ -2883,6 +2922,7 @@ class HeartbeatMessage(Packet, code=Enum_Packet.Heartbeat_Message):
 
     #: Flags.
     flags: 'HeartbeatMessageFlags' = BitField(length=2, namespace={
+        'reserved': (0, 14),
         'U': (14, 1),
         'R': (15, 1),
     })
@@ -2955,6 +2995,7 @@ class BindingRevocationMessage(Packet, code=Enum_Packet.Binding_Revocation_Messa
         'P': (0, 1),
         'V': (1, 1),
         'G': (2, 1),
+        'reserved': (3, 13),
     })
     #: Mobility options.
     options: 'list[Option]' = OptionField(
@@ -3020,6 +3061,7 @@ class LocalizedRoutingAcknowledgmentMessage(
     #: Flags.
     flags: 'LocalizedRoutingAcknowledgmentMessageFlags' = BitField(length=1, namespace={
         'U': (0, 1),
+        'reserved': (1, 7),
     })
     #: Status, c.f.,
     #: :class:`pcapkit.protocols.internet.mh.LocalizedRoutingStatus`.
@@ -3054,6 +3096,7 @@ class UpdateNotificationMessage(Packet, code=Enum_Packet.Update_Notification):
     flags: 'UpdateNotificationMessageFlags' = BitField(length=2, namespace={
         'A': (0, 1),
         'D': (1, 1),
+        'reserved': (2, 14),
     })
     #: Mobility options.
     options: 'list[Option]' = OptionField(
@@ -3123,6 +3166,7 @@ class FlowBindingMessage(Packet, code=Enum_Packet.Flow_Binding_Message):
     #: Flags.
     flags: 'FlowBindingMessageFlags' = BitField(length=1, namespace={
         'A': (0, 1),
+        'reserved': (1, 7),
     })
     #: Mobility options.
     options: 'list[Option]' = OptionField(
@@ -3176,6 +3220,7 @@ class SubscriptionResponseMessage(Packet, code=Enum_Packet.Subscription_Response
     #: Flags.
     flags: 'SubscriptionResponseMessageFlags' = BitField(length=1, namespace={
         'I': (0, 1),
+        'reserved': (1, 7),
     })
     #: Mobility options.
     options: 'list[Option]' = OptionField(
diff --git a/tests/protocols/internet/test_mh_flags_reserved_unit.py b/tests/protocols/internet/test_mh_flags_reserved_unit.py
new file mode 100644
index 0000000000..4ef547afb4
--- /dev/null
+++ b/tests/protocols/internet/test_mh_flags_reserved_unit.py
@@ -0,0 +1,192 @@
+# -*- coding: utf-8 -*-
+"""MH flag words keep their reserved bits on rebuild.
+
+GitHub issue #1418: 24 MH ``flags`` bit fields named only some of their bits,
+and :class:`~pcapkit.corekit.fields.strings.BitField` packs an unnamed bit as
+zero, so a message, option or sub-structure whose reserved bits were set came
+back with them cleared. Each site now names a ``reserved`` sub-field, read into
+the data model (``flags_reserved`` on a message, since :attr:`MH.reserved` is
+the fixed-header octet, and ``reserved`` elsewhere) and written back by
+``make()``, where it defaults to ``0``.
+
+Every frame sets every reserved bit of its site and nothing else unusual. Each
+case builds its own octets in memory and reads no capture. :class:`MH` is
+imported inside each test, after :func:`~tests._support.reimport_once_per_class`.
+
+"""
+
+import unittest
+
+from tests._support import reimport_once_per_class
+
+#: ``site -> (Mobility Header octets, width of the reserved sub-field)``. The
+#: options ride in a Binding Refresh Request; next header is 59 throughout.
+FRAMES = {
+    'BindingRevocationMessage': ('3b0110000000010000001fff01020000', 13),
+    'FastBindingAcknowledgmentMessage': ('3b0109000000007f0000000401020000', 7),
+    'FastBindingUpdateMessage': ('3b01080000000000cfff000401020000', 12),
+    'FlowBindingMessage': ('3b011500000000010000017f01020000', 7),
+    'HandoverAcknowledgeMessage': ('3b010f00000000001f00010400000000', 5),
+    'HandoverInitiateMessage': ('3b010e00000000000f00010400000000', 4),
+    'HeartbeatMessage': ('3b010d000000fffc0000000001020000', 14),
+    'LocalizedRoutingAcknowledgmentMessage': ('3b011200000000007f00000001020000', 7),
+    'SubscriptionResponseMessage': ('3b0017000000007f', 7),
+    'UpdateNotificationMessage': ('3b0113000000000000013fff01020000', 14),
+    'DNSUpdateOption': ('3b010000000000001102007f01020000', 7),
+    'DelegatedMNPOption': ('3b010000000000003706ff18c0000200', 7),
+    'DynamicIPMulticastSelectorOption': ('3b0100000000000036048f7f00000000', 7),
+    'IPv4AddressAcknowledgementOption': ('3b010000000000001e06008300000000', 2),
+    'IPv4DHCPSupportModeOption': ('3b010000000000002702fffe01020000', 15),
+    'IPv4HomeAddressReplyOption': ('3b010000000000002506008300000000', 2),
+    'IPv4HomeAddressRequestOption': ('3b01000000000000240683ff00000000', 10),
+    'IPv4TrafficOffloadSelectorOption': ('3b0100000000000035047fffffff0000', 31),
+    'MAGMultipathBindingOption': ('3b010000000000003f060100013fffff', 22),
+    'NATDetectionOption': ('3b010000000000001f067fff00000000', 15),
+    'RedirectOption': ('3b010000000000002f067fffc0000201', 14),
+    'TransientBindingOption': ('3b010000000000002b02fe0001020000', 7),
+    # CGA Parameters option carrying one CGA parameter with a Multi-Prefix extension
+    'MultiPrefixExtension': ('3b060000000000000c2b086fca5e10b200c99c8ce00164277c08'
+                             '0000000000000001013000' '0012000c7fffffff0000000000000001'
+                             '010100', 31),
+    # Quality-of-Service option carrying one per-session bit-rate attribute
+    'PerSessionBitRateAttribute': ('3b020000000000003a0e00000000000003063fff000003e8', 14),
+}
+
+MESSAGES = {
+    'BindingRevocationMessage': 'Binding_Revocation_Message',
+    'FastBindingAcknowledgmentMessage': 'Fast_Binding_Acknowledgment',
+    'FastBindingUpdateMessage': 'Fast_Binding_Update',
+    'FlowBindingMessage': 'Flow_Binding_Message',
+    'HandoverAcknowledgeMessage': 'Handover_Acknowledge_Message',
+    'HandoverInitiateMessage': 'Handover_Initiate_Message',
+    'HeartbeatMessage': 'Heartbeat_Message',
+    'LocalizedRoutingAcknowledgmentMessage': 'Localized_Routing_Acknowledgment',
+    'SubscriptionResponseMessage': 'Subscription_Response',
+    'UpdateNotificationMessage': 'Update_Notification',
+}
+
+#: ``site -> (option name, extra make() arguments)``.
+OPTIONS = {
+    'DNSUpdateOption': ('DNS_UPDATE_TYPE', {}),
+    'DelegatedMNPOption': ('Delegated_Mobile_Network_Prefix', {'prefix': '192.0.2.0', 'prefix_length': 24}),
+    'DynamicIPMulticastSelectorOption': ('Dynamic_IP_Multicast_Selector', {}),
+    'IPv4AddressAcknowledgementOption': ('IPv4_Address_Acknowledgement', {}),
+    'IPv4DHCPSupportModeOption': ('IPv4_DHCP_Support_Mode', {}),
+    'IPv4HomeAddressReplyOption': ('IPv4_Home_Address_Reply', {}),
+    'IPv4HomeAddressRequestOption': ('IPv4_Home_Address_Request', {}),
+    'IPv4TrafficOffloadSelectorOption': ('IPv4_Traffic_Offload_Selector', {}),
+    'MAGMultipathBindingOption': ('MAG_Multipath_Binding', {}),
+    'NATDetectionOption': ('NAT_Detection', {}),
+    'RedirectOption': ('Redirect_Mobility_Option', {'ipv4': '192.0.2.1'}),
+    'TransientBindingOption': ('Transient_Binding', {}),
+}
+
+
+class TestMHFlagsReserved(unittest.TestCase):
+    """Pin the reserved bits of every MH ``flags`` bit field."""
+
+    def setUp(self) -> None:
+        reimport_once_per_class(self)
+
+    @staticmethod
+    def _parse(octets: 'bytes') -> 'object':
+        import io
+
+        from pcapkit.protocols.internet.mh import MH
+
+        return MH(io.BytesIO(octets), len(octets), extension=True)
+
+    @staticmethod
+    def _site(info: 'object', site: 'str') -> 'tuple[object, str]':
+        """Return the data model holding the site's reserved bits and its name."""
+        from pcapkit.const.mh.cga_extension import CGAExtension
+        from pcapkit.const.mh.option import Option
+        from pcapkit.const.mh.qos_attribute import QoSAttribute
+
+        if site in MESSAGES:
+            return info, 'flags_reserved'
+        if site in OPTIONS:
+            return info.options[Option[OPTIONS[site][0]]], 'reserved'  # type: ignore[attr-defined]
+        if site == 'MultiPrefixExtension':
+            param = info.options[Option.CGA_Parameters].parameters[0]  # type: ignore[attr-defined]
+            return param.extensions[CGAExtension.Multi_Prefix], 'reserved'
+        qos = info.options[Option.Quality_of_Service]  # type: ignore[attr-defined]
+        return qos.attributes[QoSAttribute.Per_Session_Agg_Max_DL_Bit_Rate], 'reserved'
+
+    @staticmethod
+    def _make(site: 'str', **reserved: 'int') -> 'bytes':
+        """Build the site through ``make()``, passing ``reserved`` through."""
+        from pcapkit.const.mh.cga_extension import CGAExtension
+        from pcapkit.const.mh.cga_type import CGAType
+        from pcapkit.const.mh.option import Option
+        from pcapkit.const.mh.packet import Packet
+        from pcapkit.const.mh.qos_attribute import QoSAttribute
+        from pcapkit.const.reg.transtype import TransType
+        from pcapkit.protocols.data.internet.mh import CGAParameter
+        from pcapkit.protocols.internet.mh import MH
+
+        if site in MESSAGES:
+            data = {'flags_reserved': reserved['value']} if reserved else {}
+            return bytes(MH(next=TransType.IPv6_NoNxt, type=Packet[MESSAGES[site]], data=data))
+
+        args = {'reserved': reserved['value']} if reserved else {}
+        if site in OPTIONS:
+            name, extra = OPTIONS[site]
+            option = (Option[name], dict(extra, **args))
+        elif site == 'MultiPrefixExtension':
+            param = CGAParameter(modifier=CGAType.Tag_086F_CA5E_10B2_00C9_9C8C_E001_6427_7C08,
+                                 prefix=1, collision_count=1, public_key=b'\x30\x00',
+                                 extensions=[(CGAExtension.Multi_Prefix, dict(args, prefixes=[1]))])
+            option = (Option.CGA_Parameters, {'parameters': [param]})
+        else:
+            option = (Option.Quality_of_Service, {'attributes': [
+                (QoSAttribute.Per_Session_Agg_Max_DL_Bit_Rate, dict(args, rate=1000))]})
+        return bytes(MH(next=TransType.IPv6_NoNxt, type=Packet.Binding_Refresh_Request,
+                        data={'options': [option]}))
+
+    def test_every_site_is_covered(self) -> None:
+        self.assertEqual(len(FRAMES), 24)
+        self.assertEqual(set(FRAMES), set(MESSAGES) | set(OPTIONS)
+                         | {'MultiPrefixExtension', 'PerSessionBitRateAttribute'})
+
+    def test_reserved_bits_are_read(self) -> None:
+        for site, (frame, width) in FRAMES.items():
+            with self.subTest(site=site):
+                model, attr = self._site(self._parse(bytes.fromhex(frame)).info, site)  # type: ignore[attr-defined]
+                self.assertEqual(type(model).__name__, site)
+                self.assertEqual(getattr(model, attr), (1 << width) - 1)
+
+    def test_from_data_rebuilds_byte_for_byte(self) -> None:
+        from pcapkit.protocols.internet.mh import MH
+
+        for site, (frame, _) in FRAMES.items():
+            with self.subTest(site=site):
+                octets = bytes.fromhex(frame)
+                rebuilt = MH.from_data(self._parse(octets).info)  # type: ignore[attr-defined]
+                self.assertEqual(bytes(rebuilt).hex(), octets.hex())
+
+    def test_make_writes_the_reserved_bits(self) -> None:
+        for site, (frame, width) in FRAMES.items():
+            with self.subTest(site=site):
+                built = self._make(site, value=(1 << width) - 1)
+                self.assertEqual(built.hex(), frame)
+                model, attr = self._site(self._parse(built).info, site)  # type: ignore[attr-defined]
+                self.assertEqual(getattr(model, attr), (1 << width) - 1)
+
+    def test_make_defaults_the_reserved_bits_to_zero(self) -> None:
+        for site in FRAMES:
+            with self.subTest(site=site):
+                model, attr = self._site(self._parse(self._make(site)).info, site)  # type: ignore[attr-defined]
+                self.assertEqual(getattr(model, attr), 0)
+
+    def test_make_rejects_a_value_wider_than_the_reserved_bits(self) -> None:
+        from pcapkit.utilities.exceptions import FieldValueError
+
+        for site, (_, width) in FRAMES.items():
+            with self.subTest(site=site):
+                with self.assertRaisesRegex(FieldValueError, r"subfield 'reserved' value \d+ needs"):
+                    self._make(site, value=1 << width)
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/tests/protocols/internet/test_mh_unit.py b/tests/protocols/internet/test_mh_unit.py
index dbae981fda..9edb916ee8 100644
--- a/tests/protocols/internet/test_mh_unit.py
+++ b/tests/protocols/internet/test_mh_unit.py
@@ -425,7 +425,7 @@ def test_mh_option_readers_cover_known_options_and_guards(self) -> None:
         ext = proto._read_cga_extensions([
             schema.UnknownExtension(type=CGAExtension.Exp_FFFD, length=2, data=b'xx'),
             schema.MultiPrefixExtension(type=CGAExtension.Multi_Prefix, length=20,
-                                        flags={'P': 1}, prefixes=[1, 2]),
+                                        flags={'P': 1, 'reserved': 0}, prefixes=[1, 2]),
         ])
         self.assertEqual(list(ext.keys()), [CGAExtension.Exp_FFFD, CGAExtension.Multi_Prefix])
         self.assertEqual(proto._read_ext_none(
@@ -434,7 +434,7 @@ def test_mh_option_readers_cover_known_options_and_guards(self) -> None:
         ).data, b'yy')
         self.assertTrue(proto._read_ext_multiprefix(
             schema.MultiPrefixExtension(type=CGAExtension.Multi_Prefix, length=20,
-                                        flags={'P': 1}, prefixes=[1]),
+                                        flags={'P': 1, 'reserved': 0}, prefixes=[1]),
             extensions=ext,
         ).flag)
 
@@ -580,7 +580,7 @@ def test_mh_option_constructors_cover_known_options_and_dispatch(self) -> None:
         self.assertTrue(proto._make_ext_multiprefix(
             CGAExtension.Multi_Prefix,
             data.MultiPrefixExtension(type=CGAExtension.Multi_Prefix,
-                                      length=20, flag=True, prefixes=(3,)),
+                                      length=20, flag=True, reserved=0, prefixes=(3,)),
         ).flags['P'])
         ext_list, ext_len = proto._make_cga_extensions([
             b'\xff\xfd\x00\x02xx',
@@ -929,7 +929,7 @@ def header(type_: Packet) -> SimpleNamespace:
         # "the requested time in seconds", unlike the BU/BA lifetime's units
         # of 4 seconds, so it is read unscaled (c.f. #493).
         fbu = proto._read_msg_fbu(SimpleNamespace(seq=0x1234,
-                                                 flags={'A': 1, 'H': 1, 'L': 0, 'K': 1},
+                                                 flags={'A': 1, 'H': 1, 'L': 0, 'K': 1, 'reserved': 0},
                                                  lifetime=10, options=[]),
                                   header=header(Packet.Fast_Binding_Update))
         self.assertEqual(fbu.seq, 0x1234)
@@ -944,7 +944,7 @@ def header(type_: Packet) -> SimpleNamespace:
         # which is *not* what StatusCode(1) means, hence the module-local enum.
         # The Lifetime here is likewise "the granted lifetime ... in seconds"
         # (c.f. #493), so it too is read unscaled.
-        fback = proto._read_msg_fback(SimpleNamespace(status=1, flags={'K': 1}, seq=0x1234,
+        fback = proto._read_msg_fback(SimpleNamespace(status=1, flags={'K': 1, 'reserved': 0}, seq=0x1234,
                                                      lifetime=10, options=[]),
                                      header=header(Packet.Fast_Binding_Acknowledgment))
         self.assertEqual(fback.status, 1)
@@ -969,7 +969,7 @@ def header(type_: Packet) -> SimpleNamespace:
         # RFC 5568, section 6.2.1.1 and RFC 5949, section 6.1.1.
         hi = proto._read_msg_hi(SimpleNamespace(
             seq=0x0102,
-            flags={'S': 1, 'U': 0, 'P': 1, 'F': 0},
+            flags={'S': 1, 'U': 0, 'P': 1, 'F': 0, 'reserved': 0},
             code=HandoverInitiateStatus.FBU_whose_source_IP_address_is_not_PCoA,
             options=[],
         ), header=header(Packet.Handover_Initiate_Message))
@@ -983,7 +983,7 @@ def header(type_: Packet) -> SimpleNamespace:
         # RFC 5568, section 6.2.1.2 and RFC 5949, section 6.1.2.
         hack = proto._read_msg_hack(SimpleNamespace(
             seq=0x0102,
-            flags={'U': 1, 'P': 0, 'F': 1},
+            flags={'U': 1, 'P': 0, 'F': 1, 'reserved': 0},
             code=HandoverACKStatus.Handover_Accepted_NCoA_assigned,
             options=[],
         ), header=header(Packet.Handover_Acknowledge_Message))
@@ -998,9 +998,9 @@ def header(type_: Packet) -> SimpleNamespace:
                                        lifetime=datetime.timedelta(seconds=40), options=[])
         self.assertEqual(made_fbu.seq, 7)
         self.assertEqual(made_fbu.lifetime, 40)
-        self.assertEqual(made_fbu.flags, {'A': True, 'H': True, 'L': False, 'K': True})
+        self.assertEqual(made_fbu.flags, {'A': True, 'H': True, 'L': False, 'K': True, 'reserved': 0})
         self.assertEqual(proto._make_msg_fbu(SimpleNamespace(
-            seq=8, ack=False, home=True, lla_compat=True, key_mngt=False,
+            seq=8, ack=False, home=True, lla_compat=True, key_mngt=False, flags_reserved=0,
             lifetime=datetime.timedelta(seconds=8), options=[],
         )).seq, 8)
 
@@ -1017,7 +1017,7 @@ def header(type_: Packet) -> SimpleNamespace:
         ).status, 129)
         self.assertEqual(proto._make_msg_fback(SimpleNamespace(
             status=FastBindingAcknowledgmentStatus.Fast_Binding_Update_accepted_but_NCoA_is_invalid,
-            key_mngt=False, seq=10, lifetime=datetime.timedelta(seconds=8), options=[],
+            key_mngt=False, flags_reserved=0, seq=10, lifetime=datetime.timedelta(seconds=8), options=[],
         )).seq, 10)
 
         self.assertEqual(proto._make_msg_fna(None, options=[]).options, ['made'])
@@ -1031,9 +1031,9 @@ def header(type_: Packet) -> SimpleNamespace:
                                      forward=False, code=1, options=[])
         self.assertEqual(made_hi.seq, 11)
         self.assertEqual(made_hi.code, HandoverInitiateStatus.FBU_whose_source_IP_address_is_not_PCoA)
-        self.assertEqual(made_hi.flags, {'S': True, 'U': False, 'P': True, 'F': False})
+        self.assertEqual(made_hi.flags, {'S': True, 'U': False, 'P': True, 'F': False, 'reserved': 0})
         self.assertEqual(proto._make_msg_hi(SimpleNamespace(
-            seq=12, assign=False, buffer=True, proxy=False, forward=True,
+            seq=12, assign=False, buffer=True, proxy=False, forward=True, flags_reserved=0,
             code=HandoverInitiateStatus.All_available_context_transferred, options=[],
         )).seq, 12)
 
@@ -1041,9 +1041,9 @@ def header(type_: Packet) -> SimpleNamespace:
                                          code=130, options=[])
         self.assertEqual(made_hack.seq, 13)
         self.assertEqual(made_hack.code, HandoverACKStatus.Insufficient_resources)
-        self.assertEqual(made_hack.flags, {'U': True, 'P': False, 'F': True})
+        self.assertEqual(made_hack.flags, {'U': True, 'P': False, 'F': True, 'reserved': 0})
         self.assertEqual(proto._make_msg_hack(SimpleNamespace(
-            seq=14, buffer=False, proxy=True, forward=False,
+            seq=14, buffer=False, proxy=True, forward=False, flags_reserved=0,
             code=HandoverACKStatus.Handover_Accepted_use_PCoA, options=[],
         )).seq, 14)
 
@@ -1080,12 +1080,12 @@ def header(type_: Packet) -> SimpleNamespace:
         # -- read side: wire lifetime=100 --
 
         fbu = proto._read_msg_fbu(SimpleNamespace(
-            seq=1, flags={'A': 1, 'H': 1, 'L': 0, 'K': 0}, lifetime=100, options=[],
+            seq=1, flags={'A': 1, 'H': 1, 'L': 0, 'K': 0, 'reserved': 0}, lifetime=100, options=[],
         ), header=header(Packet.Fast_Binding_Update))
         self.assertEqual(fbu.lifetime, datetime.timedelta(seconds=100))
 
         fback = proto._read_msg_fback(SimpleNamespace(
-            status=0, flags={'K': 0}, seq=1, lifetime=100, options=[],
+            status=0, flags={'K': 0, 'reserved': 0}, seq=1, lifetime=100, options=[],
         ), header=header(Packet.Fast_Binding_Acknowledgment))
         self.assertEqual(fback.lifetime, datetime.timedelta(seconds=100))