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

XML
HTML
TXT

Registries Included Below

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][RFC 6233][RFC 7356][RFC 8918][RFC 9885]
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

CSV
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 [RFC9502, Section 6.1]
127 IPv6 Algorithm Prefix Reachability n y n n n [RFC9502, 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]
Available Formats

CSV
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
[RFC 8500][RFC 9885]
Available Formats

CSV
Type Description MP Reference
0 Reserved [RFC 8500]
1-17 Unassigned
18 Traffic Engineering Metric n [RFC8500, 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][RFC 5316][RFC 7370][RFC 8668][RFC 9885]
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

CSV
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 [RFC9843, 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 [RFC9352, Section 8.1]
44 SRv6 LAN End.X SID y y y y y y y [RFC9352, 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][RFC 9667][RFC 9650]
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

CSV
Value Name L2BM Reference
0x1 Local Protection Available N [RFC 5029]
0x2 Link Excluded from Local Protection N [RFC 5029]
0x4 Local Edge Enabled for Flooding (LEEF) N [RFC 9667]

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][RFC 7370][RFC 9352][RFC 9885]
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

CSV
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 [RFC9352, Section 7.2]
6 Flexible Algorithm Prefix Metric (FAPM) n n n y y y y n [RFC9350, 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]
Available Formats

CSV
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) [RFC9352, Section 6]
5 U-Flag [RFC9929, Section 3.2]
6 UP-Flag [RFC9929, 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]
Available Formats

CSV
Type Description Reference
0 Reserved [RFC 7176]
1 GMAC-ADDR [RFC 7176]
2 GIP-ADDR [RFC 7176]
3 GIPV6-ADDR [RFC 7176]
4 GLMAC-ADDR [RFC 7176]
5 GLIP-ADDR [RFC 7176]
6 GLIPV6-ADDR [RFC 7176]
7-254 Unassigned
255 Reserved [RFC 7176]

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]
Available Formats

CSV
Value Group Address Type Code Reference
0 Reserved [RFC 7176]
1 VLAN-FLAGs [RFC 7176]
2 Enabled-VLANs [RFC 7176]
3 AppointedFwrdrs [RFC 7176]
4 SPB-MCID [RFC 6329]
5 SPB-Digest [RFC 6329]
6 SPB-B-VID [RFC 6329]
7 PORT-TRILL-VER [RFC 7176]
8 VLANs-Appointed [RFC 7176]
9-254 Unassigned
255 Reserved [RFC 7176]

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][RFC 9885]
Available Formats

CSV
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
[RFC 7981][RFC 9885]
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

CSV
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 [RFC9352, Section 2]
26 Flexible Algorithm Definition (FAD) n [RFC9350, Section 5.1]
27 IS-IS Area Leader n [RFC 9667]
28 IS-IS Dynamic Flooding n [RFC 9667]
29 IP Algorithm n [RFC9502, Section 5.1]
30 MP-TLV Support for TLVs with Implicit Support n [RFC9885, 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][RFC 9885]
Available Formats

CSV
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]
Available Formats

CSV
Type Description Reference
0 Unassigned
1 O-flag [RFC9352, 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]
Available Formats

CSV
ID Value Description Allowed in Instance zero (y/n) Reference
0 Reserved [RFC 6823]
1 TRILL n [RFC 7357]
2-65535 Unassigned

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
[RFC 8401][RFC 9885]
Available Formats

CSV
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
[RFC 8667][RFC 9885]
Available Formats

CSV
Type Description MP Reference
0 Reserved [RFC 8667]
1 SID/Label n [RFC 8667]
2 Unassigned
3 Prefix Segment Identifier n [RFC 8667]
4-255 Unassigned

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
[RFC 9479][RFC 9885]
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

CSV

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
[RFC 9479][RFC 9885]
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

CSV
Value Description MP Reference
0-3 Unassigned
4 Link Local/Remote Identifiers n [RFC 5307]
5 Unassigned
6 IPv4 interface address n [RFC 5305]
7 Unassigned
8 IPv4 neighbor address n [RFC 5305]
9-11 Unassigned
12 IPv6 Interface Address n [RFC 6119]
13 IPv6 Neighbor Address n [RFC 6119]
14-255 Unassigned

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][RFC 9885]
Available Formats

CSV
Type Description 5 43 44 MP Reference
0 Reserved [RFC 9352]
1 SRv6 SID Structure y y y n [RFC 9352]
2-255 Unassigned

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]
Available Formats

CSV
Value Description Reference
0 D-flag [RFC9352, 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]
Available Formats

CSV
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]
Available Formats

CSV
Value Description Reference
0 B-flag [RFC9352, Section 8.1]
1 S-flag [RFC9352, Section 8.1]
2 P-flag [RFC9352, 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
[RFC 9350][RFC 9885]
Available Formats

CSV
Type Description MP Reference
0 Reserved [RFC 9350]
1 Flexible Algorithm Exclude Admin Group n [RFC9350, Section 6.1]
2 Flexible Algorithm Include-Any Admin Group n [RFC9350, Section 6.2]
3 Flexible Algorithm Include-All Admin Group n [RFC9350, Section 6.3]
4 Flexible Algorithm Definition Flags n [RFC9350, Section 6.4]
5 Flexible Algorithm Exclude SRLG n [RFC9350, Section 6.5]
6 IS-IS Exclude Minimum Bandwidth n [RFC9843, Section 3.1.1]
7 IS-IS Exclude Maximum Delay n [RFC9843, Section 3.1.2]
8 IS-IS Reference Bandwidth n [RFC9843, Section 4.1.3.1]
9 IS-IS Bandwidth Threshold n [RFC9843, Section 4.1.3.2]
10 Flexible Algorithm Exclude Reverse Admin Group n [RFC9917, Section 5]
11 Flexible Algorithm Include-Any Reverse Admin Group n [RFC9917, Section 6]
12 Flexible Algorithm Include-All Reverse Admin Group n [RFC9917, 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
[RFC 9377][RFC 9885]
Available Formats

CSV
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]
Available Formats

CSV
Value Name Reference
0 Unassigned
1 Area Proxy System Identifier [RFC 9666]
2 Area SID [RFC 9666]
3-255 Unassigned

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]
Available Formats

CSV
Type Description Reference
0 Reserved [RFC 9681]
1 LSP Burst Size [RFC 9681]
2 LSP Transmission Interval [RFC 9681]
3 LSPs per PSNP [RFC 9681]
4 Flags [RFC 9681]
5 PSNP Interval [RFC 9681]
6 Receive Window [RFC 9681]
7-255 Unassigned

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]
Note
In order to minimize encoding space, a new allocation should pick the
smallest available value.
Available Formats

CSV
Bit # Description Reference
0 Ordered acknowledgment (O-flag) [RFC 9681]
1-63 Unassigned