IS-IS TLV Codepoints
Created
- 2003-05-06
Last Updated
- 2026-05-20
Note
For IS-IS registries and value ranges maintained via the "Expert Review" RFC 8126 registration procedure, guidance for IESG-designated experts can be found in RFC 7370.
Available Formats
IS-IS Top-Level TLV Codepoints
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- Top-level TLVs for the IS-IS protocol
Reference
- RFC 3563: Cooperative Agreement Between the ISOC/IETF and ISO/IEC Joint Technical Committee 1/Sub Committee 6 (JTC1/SC6) on IS-IS Routing Protocol Development
- RFC 6233: IS-IS Registry Extension for Purges
- RFC 7356: IS-IS Flooding Scope Link State PDUs (LSPs)
- RFC 8918: Invalid TLV Handling in IS-IS
- RFC 9885: Multi-Part TLVs in IS-IS
Note
IETF SHALL keep JTC1/SC6 informed of TLV codepoint values allocated, and JTC1/SC6 SHALL refer allocation requests arising within JTC1 constituencies to the IANA registry process.
Note
Codepoints greater than 255 can only be used in PDUs designated to support extended TLVs.
Available Formats
| Value | Name | IIH | LSP | SNP | Purge | MP | Status/Reference |
|---|---|---|---|---|---|---|---|
| 0 | Reserved | ||||||
| 1 | Area Addresses | y | y | n | n | n | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002. |
| 2 | IIS Neighbors | n | y | n | n | n | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002. |
| 3 | ES Neighbors | n | y | n | n | n | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002. |
| 4 | Part. DIS | n | y | n | n | n | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002. |
| 5 | Prefix Neighbors | n | y | n | n | n | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002. |
| 6 | IIS Neighbors | y | n | n | n | n | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002. |
| 7 | Instance Identifier | y | y | y | y | y | RFC 8202 |
| 8 | Padding | y | n | n | n | n | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002. |
| 9 | LSP Entries | n | n | y | n | n | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002. |
| 10 | Authentication | y | y | y | y | n | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002.; RFC 6233 |
| 11 | ESN TLV | y | n | y | n | n | RFC 7602 |
| 12 | Opt. Checksum | y | n | y | n | n | RFC 3358 |
| 13 | Purge Originator Identification | n | n | n | y | n | RFC 6232; RFC 8918 |
| 14 | LSPBufferSize | n | y | n | n | n | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002. |
| 15 | Router-Fingerprint | y | y | n | y | n | RFC 8196 |
| 16 | Reverse Metric | y | n | n | n | n | RFC 8500 |
| 17 | IS-IS Area Node IDs | n | y | n | n | n | RFC 9667 |
| 18 | IS-IS Flooding Path | n | y | n | n | n | RFC 9667 |
| 19 | IS-IS Flooding Request | y | n | n | n | n | RFC 9667 |
| 20 | Area Proxy | n | y | n | n | y | RFC 9666 |
| 21 | Flooding Parameters TLV | y | n | y | n | y | RFC 9681 |
| 22 | Extended IS reachability | n | y | n | n | y | RFC 5305 |
| 23 | IS Neighbor Attribute | n | y | n | n | y | RFC 5311 |
| 24 | IS Alias ID | n | y | n | n | n | RFC 5311 |
| 25 | L2 Bundle Member Attributes | n | y | n | n | y | RFC 8668 |
| 26 | Unassigned | ||||||
| 27 | SRv6 Locator | n | y | n | n | y | RFC 9352 |
| 28 | Zone ID (DEPRECATED - temporarily registered 2020-11-20, allowed to expire 2025-10-15) | n | y | n | n | n | draft-ietf-lsr-isis-ttz-08 |
| 29-41 | Unassigned | ||||||
| 42 | DECnet Phase IV | y | n | n | n | n | DEC (ancient) |
| 43-65 | Unassigned | ||||||
| 66 | Lucent Proprietary | n | y | n | n | n | |
| 67-125 | Unassigned | ||||||
| 126 | IPv4 Algorithm Prefix Reachability | n | y | n | n | n | RFC 9502, Section 6.1 |
| 127 | IPv6 Algorithm Prefix Reachability | n | y | n | n | n | RFC 9502, Section 6.2 |
| 128 | IP Int. Reach | n | y | n | n | n | RFC 1195; RFC 5302 |
| 129 | Prot. Supported | y | y | n | n | n | RFC 1195 |
| 130 | IP Ext. Address | n | y | n | n | n | RFC 1195; RFC 5302 |
| 131 | IDRPI | n | y | y | n | n | RFC 1195 |
| 132 | IP Intf. Address | y | y | n | n | n | RFC 1195 |
| 133 | Illegal | n | n | n | n | n | RFC 1195 (not used) |
| 134 | Traffic Engineering router ID | n | y | n | n | n | RFC 5305 |
| 135 | Extended IP reachability | n | y | n | n | y | RFC 5305 |
| 136 | Unassigned | ||||||
| 137 | Dynamic Name | n | y | n | y | n | RFC 5301; RFC 6233 |
| 138 | GMPLS-SRLG | n | y | n | n | y | RFC 5307 |
| 139 | IPv6 SRLG | n | y | n | n | n | RFC 6119 |
| 140 | IPv6 TE Router ID | n | y | n | n | n | RFC 6119 |
| 141 | Inter-AS Reachability Information | n | y | n | n | y | RFC 9346 |
| 142 | GADDR-TLV | n | y | n | n | y | RFC 7176 |
| 143 | MT-Port-Cap-TLV | y | n | n | n | y | RFC 6165 |
| 144 | MT-Capability TLV | n | y | n | n | y | RFC 6329 |
| 145 | TRILL Neighbor TLV | y | n | n | n | n | RFC 7176 |
| 146 | Unassigned | ||||||
| 147 | MAC-RI TLV | n | y | n | n | y | RFC 6165 |
| 148 | BFD-Enabled TLV | y | n | n | n | y | RFC 6213 |
| 149 | Segment Identifier / Label Binding | n | y | n | n | y | RFC 8667 |
| 150 | Multi-Topology Segment Identifier / Label Binding | n | y | n | n | y | RFC 8667 |
| 151-160 | Unassigned | ||||||
| 161 | Flood Reflection | y | n | n | n | n | RFC 9377 |
| 162-175 | Unassigned | ||||||
| 176 | Nortel Proprietary | n | y | n | n | n | |
| 177 | Nortel Proprietary | n | y | n | n | n | |
| 178-210 | Unassigned | ||||||
| 211 | Restart TLV | y | n | n | n | n | RFC 8706 |
| 212-221 | Unassigned | ||||||
| 222 | MT-ISN | n | y | n | n | y | RFC 5120 |
| 223 | MT IS Neighbor Attribute | n | y | n | n | y | RFC 5311 |
| 224-228 | Unassigned | ||||||
| 229 | M-Topologies | y | y | n | n | n | RFC 5120 |
| 230-231 | Unassigned | ||||||
| 232 | IPv6 Intf. Addr. | y | y | n | n | n | RFC 5308 |
| 233 | IPv6 Global Interface Address TLV | y | n | n | n | n | RFC 6119 |
| 234 | Unassigned | ||||||
| 235 | MT IP. Reach | n | y | n | n | y | RFC 5120 |
| 236 | IPv6 IP. Reach | n | y | n | n | y | RFC 5308 |
| 237 | MT IPv6 IP. Reach | n | y | n | n | y | RFC 5120 |
| 238 | Application-Specific SRLG | n | y | n | n | y | RFC 9479 |
| 239 | Unassigned | ||||||
| 240 | P2P 3-Way Adj. State | y | n | n | n | n | RFC 5303 |
| 241 | Unassigned | ||||||
| 242 | IS-IS Router CAPABILITY TLV | n | y | n | n | y | RFC 7981 |
| 243 | Scope Flooding Support | y | n | n | n | n | RFC 7356 |
| 244-250 | Unassigned | ||||||
| 251 | Generic Information | n | y | n | n | y | RFC 6823 |
| 252-65535 | Unassigned |
IS-IS Authentication Type Codes
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- Type Codes for Authentication TLV (10)
Reference
- RFC 5304: IS-IS Cryptographic Authentication
Available Formats
| Value | Authentication Type Code | Reference |
|---|---|---|
| 0 | Reserved | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002. |
| 1 | Cleartext Password | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002. |
| 2 | ISO 10589 Reserved | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002. |
| 3 | Cryptographic Authentication (CRYPTO_AUTH) | RFC 5310 |
| 4-53 | Unassigned | |
| 54 | HMAC-MD5 Authentication | RFC 5304 |
| 55-254 | Unassigned | |
| 255 | Routing Domain private authentication method | ISO 10589, "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", International Standard 10589: 2002, Second Edition, 2002. |
IS-IS Sub-TLVs for Reverse Metric TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- Sub-TLVs for Reverse Metric TLV (16)
Reference
Available Formats
| Type | Description | MP | Reference |
|---|---|---|---|
| 0 | Reserved | RFC 8500 | |
| 1-17 | Unassigned | ||
| 18 | Traffic Engineering Metric | n | RFC 8500, Section 2 |
| 19-255 | Unassigned |
IS-IS Sub-TLVs for TLVs Advertising Neighbor Information
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines sub-TLVs for TLVs advertising neighbor information. The list of TLVs includes:
- Extended IS reachability (22)
- IS Neighbor Attribute (23)
- L2 Bundle Member Attributes (25)
- inter-AS reachability information (141)
- MT-ISN (222)
- MT IS Neighbor Attribute (223)
Reference
- RFC 5305: IS-IS Extensions for Traffic Engineering
- RFC 5316: ISIS Extensions in Support of Inter-Autonomous System (AS) MPLS and GMPLS Traffic Engineering
- RFC 7370: Updates to the IS-IS TLV Codepoints Registry
- RFC 8668: Advertising Layer 2 Bundle Member Link Attributes in IS-IS
- RFC 9885: Multi-Part TLVs in IS-IS
Note
Allocations within this registry require documentation of the use of the allocated value and approval by the Designated Expert assigned by the IESG.
Note
The column for TLV 25 may be marked as follows:
- y - sub-TLV may appear in TLV 25 but MUST NOT be shared by multiple L2 Bundle Members
- y(s) - sub-TLV may appear in TLV 25 and MAY be shared by multiple L2 Bundle Members
- n - sub-TLV MUST NOT appear in TLV 25
Available Formats
| Type | Description | 22 | 23 | 25 | 141 | 222 | 223 | MP | Reference |
|---|---|---|---|---|---|---|---|---|---|
| 0-2 | Unassigned | ||||||||
| 3 | Administrative group (color) | y | y | y(s) | y | y | y | n | RFC 5305 |
| 4 | Link Local/Remote Identifiers | y | y | y(s) | y | y | y | n | RFC 5307 |
| 5 | Unassigned | ||||||||
| 6 | IPv4 interface address | y | y | y(s) | y | y | y | n | RFC 5305 |
| 7 | Unassigned | ||||||||
| 8 | IPv4 neighbor address | y | y | y(s) | y | y | y | n | RFC 5305 |
| 9 | Maximum link bandwidth | y | y | y(s) | y | y | y | n | RFC 5305 |
| 10 | Maximum reservable link bandwidth | y | y | y(s) | y | y | y | n | RFC 5305 |
| 11 | Unreserved bandwidth | y | y | y(s) | y | y | y | n | RFC 5305 |
| 12 | IPv6 Interface Address | y | y | y(s) | y | y | y | n | RFC 6119 |
| 13 | IPv6 Neighbor Address | y | y | y(s) | y | y | y | n | RFC 6119 |
| 14 | Extended Administrative Group | y | y | y(s) | y | y | y | n | RFC 7308 |
| 15 | Link MSD | y | y | y | y | y | y | y | RFC 8491 |
| 16 | Application-Specific Link Attributes | y | y | y(s) | y | y | y | y | RFC 9479 |
| 17 | Generic Metric | y | y | y | y | y | y | n | RFC 9843, Section 2.1 |
| 18 | TE Default metric | y | y | y(s) | y | y | y | n | RFC 5305 |
| 19 | Link-attributes | y | y | y(s) | y | y | y | n | RFC 5029 |
| 20 | Link Protection Type | y | y | y(s) | y | y | y | n | RFC 5307 |
| 21 | Interface Switching Capability Descriptor | y | y | y(s) | y | y | y | y | RFC 5307 |
| 22 | Bandwidth Constraints | y | y | y(s) | y | y | y | n | RFC 4124 |
| 23 | Unconstrained TE LSP Count (sub-)TLV | y | y | y(s) | y | y | y | n | RFC 5330 |
| 24 | Remote AS Number | n | n | n | y | n | n | n | RFC 9346 |
| 25 | IPv4 Remote ASBR Identifier | n | n | n | y | n | n | n | RFC 9346 |
| 26 | IPv6 Remote ASBR Identifier | n | n | n | y | n | n | n | RFC 9346 |
| 27 | Interface Adjustment Capability Descriptor (IACD) | y | y | y(s) | y | y | y | y | RFC 6001 |
| 28 | MTU | y | y | n | n | y | y | n | RFC 7176 |
| 29 | SPB-Metric | y | y | y(s) | n | y | y | n | RFC 6329 |
| 30 | SPB-A-OALG | y | y | y(s) | n | y | y | y | RFC 6329 |
| 31 | Adjacency Segment Identifier | y | y | n | y | y | y | n | RFC 8667 |
| 32 | LAN Adjacency Segment Identifier | y | y | n | y | y | y | n | RFC 8667 |
| 33 | Unidirectional Link Delay | y | y | y | y | y | y | n | RFC 8570 |
| 34 | Min/Max Unidirectional Link Delay | y | y | y | y | y | y | n | RFC 8570 |
| 35 | Unidirectional Delay Variation | y | y | y | y | y | y | n | RFC 8570 |
| 36 | Unidirectional Link Loss | y | y | y | y | y | y | n | RFC 8570 |
| 37 | Unidirectional Residual Bandwidth | y | y | y | y | y | y | n | RFC 8570 |
| 38 | Unidirectional Available Bandwidth | y | y | y | y | y | y | n | RFC 8570 |
| 39 | Unidirectional Utilized Bandwidth | y | y | y | y | y | y | n | RFC 8570 |
| 40 | RTM Capability | y | y | n | n | y | y | n | RFC 8169 |
| 41 | L2 Bundle Member Adj-SID | n | n | y | n | n | n | y | RFC 8668 |
| 42 | L2 Bundle Member LAN Adj-SID | n | n | y | n | n | n | y | RFC 8668 |
| 43 | SRv6 End.X SID | y | y | y | y | y | y | y | RFC 9352, Section 8.1 |
| 44 | SRv6 LAN End.X SID | y | y | y | y | y | y | y | RFC 9352, Section 8.2 |
| 45 | IPv6 Local ASBR Identifier | n | n | n | y | n | n | n | RFC 9346 |
| 46-160 | Unassigned | ||||||||
| 161 | Flood Reflector Adjacency | y | y | n | y | y | y | n | RFC 9377 |
| 162-249 | Unassigned | ||||||||
| 250-254 | Reserved for Cisco-specific extensions | ||||||||
| 255 | Reserved for future expansion |
IS-IS Neighbor Link-Attribute Bit Values
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines bit values for the Link-attributes sub-TLV (19) advertised in TLVs advertising neighbor information. These TLVs are listed in the description of the “IS-IS Sub-TLVs for TLVs Advertising Neighbor Information” registry.
Reference
- RFC 5029: Definition of an IS-IS Link Attribute Sub-TLV
- RFC 9667: Dynamic Flooding on Dense Graphs
- RFC 9650: Revision to Registration Procedures for IS-IS Neighbor Link-Attribute Bit Values
Note
The "L2BM" column indicates applicability to the L2 Bundle Member Attributes TLV. The options for the "L2BM" column are:
- Y - This bit MAY appear in the L2 Bundle Member Attributes TLV.
- N - This bit MUST NOT appear in the L2 Bundle Member Attributes TLV.
Available Formats
IS-IS Sub-TLVs for TLVs Advertising Prefix Reachability
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines sub-TLVs for TLVs advertising prefix reachability. The list of TLVs includes:
- SRv6 Locator (27)
- IPv4 Algorithm Prefix Reachability (126)
- IPv6 Algorithm Prefix Reachability (127)
- Extended IP reachability (135)
- MT IP Reach (235)
- IPv6 IP Reach (236)
- MT IPv6 IP Reach (237)
Reference
- RFC 5305: IS-IS Extensions for Traffic Engineering
- RFC 7370: Updates to the IS-IS TLV Codepoints Registry
- RFC 9352: IS-IS Extensions to Support Segment Routing over the IPv6 Data Plane
- RFC 9885: Multi-Part TLVs in IS-IS
Note
Allocations within this registry require documentation of the use of the allocated value and approval by the Designated Expert assigned by the IESG.
Available Formats
| Type | Description | 27 | 126 | 127 | 135 | 235 | 236 | 237 | MP | Reference |
|---|---|---|---|---|---|---|---|---|---|---|
| 0 | Unassigned | |||||||||
| 1 | 32-bit Administrative Tag Sub-TLV | y | y | y | y | y | y | y | y | RFC 5130 |
| 2 | 64-bit Administrative Tag Sub-TLV | y | y | y | y | y | y | y | y | RFC 5130 |
| 3 | Prefix Segment Identifier | n | n | n | y | y | y | y | n | RFC 8667 |
| 4 | Prefix Attribute Flags | y | y | y | y | y | y | y | n | RFC 7794 |
| 5 | SRv6 End SID | y | n | n | n | n | n | n | y | RFC 9352, Section 7.2 |
| 6 | Flexible Algorithm Prefix Metric (FAPM) | n | n | n | y | y | y | y | n | RFC 9350, Section 8 |
| 7-10 | Unassigned | |||||||||
| 11 | IPv4 Source Router ID | y | y | y | y | y | y | y | n | RFC 7794 |
| 12 | IPv6 Source Router ID | y | y | y | y | y | y | y | n | RFC 7794 |
| 13-31 | Unassigned | |||||||||
| 32 | BIER Info | n | n | n | y | y | y | y | y | RFC 8401 |
| 33-255 | Unassigned |
IS-IS Bit Values for Prefix Attribute Flags Sub-TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines bit values for the Prefix Attribute Flags (4) sub-TLV advertised in Prefix Reachability TLVs. These TLVs are listed in the description of the "IS-IS Sub-TLVs for TLVs Advertising Prefix Reachability” registry.
Reference
- RFC 7794: IS-IS Prefix Attributes for Extended IPv4 and IPv6 Reachability
Available Formats
| Bit # | Name | Reference |
|---|---|---|
| 0 | External Prefix Flag (X-flag) | RFC 7794 |
| 1 | Re-advertisement Flag (R-flag) | RFC 7794 |
| 2 | Node Flag (N-flag) | RFC 7794 |
| 3 | ELC Flag (E-flag) | RFC 9088 |
| 4 | Anycast Flag (A-flag) | RFC 9352, Section 6 |
| 5 | U-Flag | RFC 9929, Section 3.2 |
| 6 | UP-Flag | RFC 9929, Section 3.2 |
IS-IS Group Address Type Codes for GADDR-TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines Group Address Type Codes for the GADDR-TLV (142).
Reference
- RFC 7176: Transparent Interconnection of Lots of Links (TRILL) Use of IS-IS
Available Formats
IS-IS Sub-TLVs for MT-Port-Cap-TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines sub-TLVs for the MT-Port-Cap-TLV (143).
Reference
- RFC 7176: Transparent Interconnection of Lots of Links (TRILL) Use of IS-IS
Available Formats
IS-IS Sub-TLVs for MT-Capability TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines sub-TLVs for the MT-Capability TLV (144).
Reference
- RFC 6329: IS-IS Extensions Supporting IEEE 802.1aq Shortest Path Bridging
- RFC 9885: Multi-Part TLVs in IS-IS
Available Formats
| Value | Group Address Type Code | MP | Reference |
|---|---|---|---|
| 0 | Reserved | RFC 6329 | |
| 1 | SPB-Inst | n | RFC 6329 |
| 2 | SPB-I-OALG | y | RFC 6329 |
| 3 | SPBM-SI | y | RFC 6329 |
| 4 | SPBV-ADDR | y | RFC 6329 |
| 5 | Unassigned | ||
| 6 | NICKNAME | y | RFC 7176 |
| 7 | TREES | n | RFC 7176 |
| 8 | TREE-RT-IDs | y | RFC 7176 |
| 9 | TREE-USE-IDs | y | RFC 7176 |
| 10 | INT-VLAN | y | RFC 7176 |
| 11-12 | Unassigned | ||
| 13 | TRILL-VER | n | RFC 7176 |
| 14 | VLAN-GROUP | y | RFC 7176 |
| 15 | INT-LABEL | y | RFC 7176 |
| 16 | RBCHANNELS | y | RFC 7176 |
| 17 | AFFINITY | y | RFC 7176 |
| 18 | LABEL-GROUP | y | RFC 7176 |
| 19-20 | Unassigned | ||
| 21 | Topology sub-TLV | y | RFC 7813 |
| 22 | Hop sub-TLV | n | RFC 7813 |
| 23 | Bandwidth Constraint sub-TLV | n | RFC 7813 |
| 24 | Bandwidth Assignment sub-TLV | n | RFC 7813 |
| 25 | Timestamp sub-TLV | n | RFC 7813 |
| 26-254 | Unassigned | ||
| 255 | Reserved | RFC 6329 |
IS-IS Sub-TLVs for IS-IS Router CAPABILITY TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines sub-TLVs for the IS-IS Router CAPABILITY TLV (242).
Reference
Note
Allocations within this registry require documentation of the use of the allocated value and approval by the Designated Expert assigned by the IESG.
Available Formats
| Value | Description | MP | Reference |
|---|---|---|---|
| 0 | Reserved | ||
| 1 | TE Node Capability Descriptor | n | RFC 5073 |
| 2 | Segment Routing Capability | n | RFC 8667 |
| 3 | TE-MESH-GROUP TLV (IPv4) | y | RFC 4972 |
| 4 | TE-MESH-GROUP TLV (IPv6) | y | RFC 4972 |
| 5 | PCED sub-TLV | n | RFC 5089 |
| 6 | NICKNAME | y | RFC 7176 |
| 7 | TREES | n | RFC 7176 |
| 8 | TREE-RT-IDs | y | RFC 7176 |
| 9 | TREE-USE-IDs | y | RFC 7176 |
| 10 | INT-VLAN | y | RFC 7176 |
| 11 | IPv4 TE Router ID | n | RFC 9346 |
| 12 | IPv6 TE Router ID | n | RFC 9346 |
| 13 | TRILL-VER | n | RFC 7176 |
| 14 | VLAN-GROUP | y | RFC 7176 |
| 15 | INT-LABEL | y | RFC 7176 |
| 16 | RBCHANNELS | y | RFC 7176 |
| 17 | AFFINITY | y | RFC 7176 |
| 18 | LABEL-GROUP | y | RFC 7176 |
| 19 | Segment Routing Algorithm | n | RFC 8667 |
| 20 | S-BFD Discriminators | n | RFC 7883 |
| 21 | Node-Admin-Tag | n | RFC 7917 |
| 22 | Segment Routing Local Block (SRLB) | n | RFC 8667 |
| 23 | Node MSD | y | RFC 8491 |
| 24 | Segment Routing Mapping Server Preference (SRMS Preference) | n | RFC 8667 |
| 25 | SRv6 Capabilities | n | RFC 9352, Section 2 |
| 26 | Flexible Algorithm Definition (FAD) | n | RFC 9350, Section 5.1 |
| 27 | IS-IS Area Leader | n | RFC 9667 |
| 28 | IS-IS Dynamic Flooding | n | RFC 9667 |
| 29 | IP Algorithm | n | RFC 9502, Section 5.1 |
| 30 | MP-TLV Support for TLVs with Implicit Support | n | RFC 9885, Section 7.2 |
| 31-160 | Unassigned | ||
| 161 | Flood Reflection Discovery | y | RFC 9377 |
| 162-249 | Unassigned | ||
| 250 | Flood Reduction Algorithm (TEMPORARY - registered 2026-05-20, expires 2027-05-20) | n | draft-ietf-lsr-flood-reduction-arch-01 |
| 251-255 | Unassigned |
IS-IS Sub-Sub-TLVs for SRv6 Capabilities Sub-TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines sub-sub-TLVs for the SRv6 Capabilities sub-TLV (25) advertised in the IS-IS Router CAPABILITY TLV (242).
Reference
- RFC 9352: IS-IS Extensions to Support Segment Routing over the IPv6 Data Plane
- RFC 9885: Multi-Part TLVs in IS-IS
Available Formats
| Value | Description | MP | Reference |
|---|---|---|---|
| 0 | Reserved | RFC 9352 | |
| 1-255 | Unassigned |
IS-IS SRv6 Capabilities Sub-TLV Flags
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines bit values advertised in the Flags field of the SRv6 Capabilities sub-TLV (25). This sub-TLV is advertised in the IS-IS Router CAPABILITY TLV (242).
Reference
- RFC 9352: IS-IS Extensions to Support Segment Routing over the IPv6 Data Plane
Available Formats
| Type | Description | Reference |
|---|---|---|
| 0 | Unassigned | |
| 1 | O-flag | RFC 9352, Section 2 |
| 2-15 | Unassigned |
IS-IS Application Identifiers for Generic Information TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines Application Identifiers for the Generic Information TLV (251).
Reference
- RFC 6823: Advertising Generic Information in IS-IS
Available Formats
IS-IS Sub-Sub-TLVs for BIER Info Sub-TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines sub-sub-TLV codes which may be advertised in the BIER Info sub-TLV, which is advertised in Prefix Reachability TLVs. These TLVs are listed in the description of the "IS-IS Sub-TLVs for TLVs Advertising Prefix Reachability” registry.
Reference
Available Formats
| Type | Name | MP | Reference |
|---|---|---|---|
| 0 | Unassigned | ||
| 1 | BIER MPLS Encapsulation | n | RFC 8401 |
| 2 | BIER PHP Request | n | RFC-ietf-bier-php-16 |
| 3-255 | Unassigned |
IS-IS Sub-TLVs for Segment Identifier/Label Binding TLVs
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines sub-TLVs for Segment Identifier/Label Binding TLVs. The list of TLVs includes:
- Segment Identifier/Label Binding (149) Multi-Topology Segment Identifier/Label Binding (150)
Reference
Available Formats
IS-IS Sub-Sub-TLV Codepoints for Application-Specific Link Attributes
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines sub-sub-TLV codepoints for the Application-Specific Link Attributes sub-TLV, which is advertised in TLVs advertising neighbor information. These TLVs are listed in the description of the “IS-IS Sub-TLVs for TLVs Advertising Neighbor Information” registry.
Reference
Note
For future codepoints, in cases where the document that defines the encoding is different from the document that assigns the codepoint, the encoding reference MUST be to the document that defines the encoding.
Note
If a link attribute can be advertised both as a sub-TLV of TLVs advertising neighbor information and as a sub-sub-TLV of the Application-Specific Link Attributes sub-TLV defined in RFC 9479, then the same numerical code should be assigned to the link attribute whenever possible.
Available Formats
| Type | Description | MP | Reference |
|---|---|---|---|
| 0-2 | Unassigned | ||
| 3 | Administrative group (color) | n | RFC 5305 |
| 4-8 | Unassigned | ||
| 9 | Maximum link bandwidth | n | RFC 5305 |
| 10 | Maximum reservable link bandwidth | n | RFC 5305 |
| 11 | Unreserved bandwidth | n | RFC 5305 |
| 12-13 | Unassigned | ||
| 14 | Extended Administrative Group | n | RFC 7308 |
| 15-16 | Unassigned | ||
| 17 | Generic Metric | y | RFC 9843, Section 2.1 |
| 18 | TE Default metric | n | RFC 5305 |
| 19-32 | Unassigned | ||
| 33 | Unidirectional Link Delay | n | RFC 8570 |
| 34 | Min/Max Unidirectional Link Delay | n | RFC 8570 |
| 35 | Unidirectional Delay Variation | n | RFC 8570 |
| 36 | Unidirectional Link Loss | n | RFC 8570 |
| 37 | Unidirectional Residual Bandwidth | n | RFC 8570 |
| 38 | Unidirectional Available Bandwidth | n | RFC 8570 |
| 39 | Unidirectional Utilized Bandwidth | n | RFC 8570 |
| 40-255 | Unassigned |
IS-IS Sub-TLVs for Application-Specific SRLG TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines sub-TLVs for the Application-Specific SRLG TLV (TLV 238).
Reference
Note
For future codepoints, in cases where the document that defines the encoding is different from the document that assigns the codepoint, the encoding reference MUST be to the document that defines the encoding.
Available Formats
IS-IS Sub-Sub-TLVs for SRv6 SID Sub-TLVs
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines sub-sub-TLVs for SRv6 SID sub-TLVs. This includes the following sub-TLVs:
- SRv6 End SID (5) (Advertised in SRv6 Locator TLV (27))
- SRv6 End.X SID (43) (Advertised in TLVs advertising neighbor information)
- SRv6 LAN End.X SID (44) (Advertised in TLVs advertising neighbor information)
Reference
- RFC 9352: IS-IS Extensions to Support Segment Routing over the IPv6 Data Plane
- RFC 9885: Multi-Part TLVs in IS-IS
Available Formats
IS-IS SRv6 Locator TLV Flags
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines bit values advertised in the Flags field of the SRv6 Locator TLV (27).
Reference
- RFC 9352: IS-IS Extensions to Support Segment Routing over the IPv6 Data Plane
Available Formats
| Value | Description | Reference |
|---|---|---|
| 0 | D-flag | RFC 9352, Section 7.1 |
| 1-7 | Unassigned |
IS-IS SRv6 End SID Sub-TLV Flags
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines bit values advertised in the Flags field of the SRv6 End SID sub-TLV (5), which is advertised in the SRv6 Locator TLV (27).
Reference
- RFC 9352: IS-IS Extensions to Support Segment Routing over the IPv6 Data Plane
Available Formats
| Value | Description | Reference |
|---|---|---|
| 0-7 | Unassigned |
IS-IS SRv6 Adjacency SID Sub-TLVs Flags
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines bit values advertised in the Flags field of SRv6 SID sub-TLVs associated with adjacencies. These sub-TLVs are advertised in TLVs advertising neighbor information. The list of sub-TLVs includes:
- SRv6 End.X SID (43) SRv6 LAN End.X SID (44)
Reference
- RFC 9352: IS-IS Extensions to Support Segment Routing over the IPv6 Data Plane
Available Formats
| Value | Description | Reference |
|---|---|---|
| 0 | B-flag | RFC 9352, Section 8.1 |
| 1 | S-flag | RFC 9352, Section 8.1 |
| 2 | P-flag | RFC 9352, Section 8.1 |
| 3-7 | Unassigned |
IS-IS Sub-Sub-TLVs for Flexible Algorithm Definition Sub-TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Reference
Available Formats
| Type | Description | MP | Reference |
|---|---|---|---|
| 0 | Reserved | RFC 9350 | |
| 1 | Flexible Algorithm Exclude Admin Group | n | RFC 9350, Section 6.1 |
| 2 | Flexible Algorithm Include-Any Admin Group | n | RFC 9350, Section 6.2 |
| 3 | Flexible Algorithm Include-All Admin Group | n | RFC 9350, Section 6.3 |
| 4 | Flexible Algorithm Definition Flags | n | RFC 9350, Section 6.4 |
| 5 | Flexible Algorithm Exclude SRLG | n | RFC 9350, Section 6.5 |
| 6 | IS-IS Exclude Minimum Bandwidth | n | RFC 9843, Section 3.1.1 |
| 7 | IS-IS Exclude Maximum Delay | n | RFC 9843, Section 3.1.2 |
| 8 | IS-IS Reference Bandwidth | n | RFC 9843, Section 4.1.3.1 |
| 9 | IS-IS Bandwidth Threshold | n | RFC 9843, Section 4.1.3.2 |
| 10 | Flexible Algorithm Exclude Reverse Admin Group | n | RFC 9917, Section 5 |
| 11 | Flexible Algorithm Include-Any Reverse Admin Group | n | RFC 9917, Section 6 |
| 12 | Flexible Algorithm Include-All Reverse Admin Group | n | RFC 9917, Section 7 |
| 13-255 | Unassigned |
IS-IS Sub-Sub-TLVs for Flood Reflection Discovery Sub-TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry contains assigned sub-sub-TLV identifiers for Flood Reflection Discovery purposes.
Reference
Available Formats
| Type | Description | MP | Reference |
|---|---|---|---|
| 0-160 | Unassigned | ||
| 161 | Flood Reflection Discovery Tunnel Encapsulation Attribute | n | RFC 9377 |
| 162-255 | Unassigned |
IS-IS Sub-TLVs for the Area Proxy TLV
Registration Procedure(s)
- Expert Review with RFC Required
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines sub-TLVs for the Area Proxy TLV (TLV 20).
Reference
- RFC 9666: Area Proxy for IS-IS
Available Formats
IS-IS Sub-TLVs for Flooding Parameters TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines sub-TLVs for the Flooding Parameters TLV(21).
Reference
- RFC 9681: IS-IS Fast Flooding
Available Formats
IS-IS Bit Values for Flooding Parameters Flags Sub-TLV
Registration Procedure(s)
- Expert Review
Expert(s)
- Chris Hopps, Hannes Gredler, Les Ginsberg
Description
- This registry defines bit values for the Flags sub-TLV(4) advertised in the Flooding Parameters TLV(21).
Reference
- RFC 9681: IS-IS Fast Flooding
Note
In order to minimize encoding space, a new allocation should pick the smallest available value.
Available Formats
| Bit # | Description | Reference |
|---|---|---|
| 0 | Ordered acknowledgment (O-flag) | RFC 9681 |
| 1-63 | Unassigned |