Multiprotocol Label Switching Architecture (MPLS) 2006-01-12 2025-11-04 0-191 Standards Action 192-247 RFC Required 248-251 Experimental Use Reserved, not to be assigned 252-255 Private Use Reserved, not to be assigned 0 Reserved 1 MPLS Echo Request 2 MPLS Echo Reply 3 MPLS Proxy Ping Request 4 MPLS Proxy Ping Reply 5 MPLS Relayed Echo Reply 6-247 Unassigned 248-251 Reserved for Experimental Use 252-255 Reserved for Private Use 0-191 Standards Action 192-247 RFC Required 248-251 Experimental Use Reserved, not to be assigned 252-255 Private Use Reserved, not to be assigned 0 Reserved 1 Do not reply 2 Reply via an IPv4/IPv6 UDP packet 3 Reply via an IPv4/IPv6 UDP packet with Router Alert (DEPRECATED) 4 Reply via application-level control channel 5 Reply via Specified Path 6-247 Unassigned 248-251 Reserved for Experimental Use 252-255 Reserved for Private Use 0-191 Standards Action 192-247 RFC Required 248-251 Experimental Use Reserved, not to be assigned 252-255 Private Use Reserved, not to be assigned 0 No Return Code 1 Malformed echo request received 2 One or more of the TLVs was not understood 3 Replying router is an egress for the FEC at stack-depth <RSC> 4 Replying router has no mapping for the FEC at stack-depth <RSC> 5 Downstream Mapping Mismatch (See ) 6 Upstream Interface Index Unknown (See ) 7 Reserved 8 Label switched at stack-depth <RSC> 9 Label switched but no MPLS forwarding at stack-depth <RSC> 10 Mapping for this FEC is not the given label at stack-depth <RSC> 11 No label entry at stack-depth <RSC> 12 Protocol not associated with interface at FEC stack-depth <RSC> 13 Premature termination of ping due to label stack shrinking to a single label 14 See DDMAP TLV for meaning of Return Code and Return Subcode (See ) 15 Label switched with FEC change 16 Proxy Ping not authorized 17 Proxy Ping parameters need to be modified 18 MPLS Echo Request could not be sent 19 Replying router has FEC mapping for topmost FEC 20 One or more TLVs not returned due to MTU size 21 OAM Problem/Unsupported BFD Version 22 OAM Problem/Unsupported BFD Encapsulation format 23 OAM Problem/Unsupported BFD Authentication Type 24 OAM Problem/Mismatch of BFD Authentication Key ID 25 OAM Problem/Unsupported Timestamp Format 26 OAM Problem/Unsupported Delay Mode 27 OAM Problem/Unsupported Loss Mode 28 OAM Problem/Delay variation unsupported 29 OAM Problem/Dyadic mode unsupported 30 OAM Problem/Loopback mode unsupported 31 OAM Problem/Combined mode unsupported 32 OAM Problem/Fault management signaling unsupported 33 OAM Problem/Unable to create fault management association 34 OAM Problem/PM Configuration Error 35 Mapping for this FEC is not associated with the incoming interface RFC8287, Section 7.4 36 Replying router is an egress for the address in the Egress TLV for the FEC at stack depth <RSC> 37 Replying router is egress for the FEC at the stack depth. In addition, the BUM packets are dropped on the ES corresponding to the ESI received in EVPN Ethernet Auto-Discovery sub-TLV because of the Split Horizon Group filtering. 38 Replying router is egress for the FEC at the stack depth. In addition, the BUM packets are forwarded because there is no ES corresponding to the ESI received in EVPN Ethernet Auto-Discovery sub-TLV. 39-191 Unassigned 192 Inappropriate Target FEC Stack sub-TLV present 193 Failed to establish the BFD session. The specified reverse path was not found. 194-247 Unassigned 248-251 Reserved for Experimental Use 252-255 Reserved for Private Use The Return Subcode (RSC) contains the point in the label stack where pro- cessing was terminated. If the RSC is 0, no labels were processed. Otherwise, the packet was label switched at depth RSC. The Return Code is per "Downstream Detailed Mapping TLV" (Section 3.4). This Return Code MUST be used only in the message header and MUST be set only in the MPLS echo reply message. If the Return Code is set in the MPLS echo request message, then it MUST be ignored. When this Return Code is set, each Downstream Detailed Mapping TLV MUST have an appropriate Return Code and Return Subcode. This Return Code MUST be used when there are multiple downstreams for a given node (such as Point-to-Multipoint (P2MP)or ECMP),and the node needs to return a Return Code/Return Subcode for each downstream. This Return Code MAY be used even when there is only one downstream for a given node. 0-16383 Standards Action This range is for TLVs that require an error message if not recognized. RFC9041, Section 3.1 16384-31739 RFC Required This range is for TLVs that require an error message if not recognized. RFC9041, Section 3.1 31740-31743 Experimental Use Reserved, not to be assigned. This range is for TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744-32767 First Come First Served This range is for TLVs that require an error message if not recognized. RFC9041, Section 3.1 32768-49161 Standards Action This range is for TLVs that can be silently dropped if not recognized. 49162-64507 RFC Required This range is for TLVs that can be silently dropped if not recognized. 64508-64511 Experimental Use Reserved, not to be assigned. This range is for TLVs that can be silently dropped if not recognized. 64512-65535 First Come First Served This range is for TLVs that can be silently dropped if not recognized. 0 Reserved 1 Target FEC Stack 2 Downstream Mapping (DEPRECATED) No Sub-TLVs 3 Pad No Sub-TLVs 4 LSR Capability No Sub-TLVs 5 Vendor Enterprise Number No Sub-TLVs 6 Detailed Interface and Label Stack 7 Interface and Label Stack No Sub-TLVs 8 Unassigned 9 Errored TLVs 10 Reply TOS Byte No Sub-TLVs 11 P2MP Responder Identifier 12 Echo Jitter No Sub-TLVs 13 Source ID No Sub-TLVs 14 Destination ID No Sub-TLVs 15 BFD Discriminator No Sub-TLVs 16 Reverse-path Target FEC Stack 17-19 Unassigned 20 Downstream Detailed Mapping 21 Reply Path 22 Reply TC No Sub-TLVs 23 Proxy Echo Parameters 24 Reply-to Address No Sub-TLVs 25 Upstream Neighbor Address No Sub-TLVs 26 Downstream Neighbor Address No Sub-TLVs 27 MPLS OAM Functions 28 EGRESS TLV (DEPRECATED) No Sub-TLVs 29-16383 Unassigned 16384 BFD Reverse Path Only non-multicast sub-TLVs (already defined or to be defined in the future) in the "Sub-TLVs for TLV Types 1, 16, and 21" registry at are permitted to be used in this field. Other sub-TLVs MUST NOT be used. 16385-31739 Unassigned 31740-31743 Reserved for Experimental Use Not to be assigned. This range is for TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744-32767 Unassigned 32768 Relay Node Address Stack TLV No Sub-TLVs 32769 Time To Live No Sub-TLVs 32770 Reply Mode Order TLV No Sub-TLVs 32771 Egress TLV No Sub-TLVs 32772-64507 Unassigned 64508-64511 Reserved for Experimental Use Not to be assigned. This range is for TLVs that can be silently dropped if not recognized. 64512-65535 Unassigned 0-16383 Standards Action This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 16384-31739 RFC Required This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31740-31743 Experimental Use Reserved, not to be assigned. This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744-32767 First Come First Served This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 32768-49161 Standards Action This range is for sub-TLVs that can be silently dropped if not recognized. 49162-64507 RFC Required This range is for sub-TLVs that can be silently dropped if not recognized. 64508-64511 Experimental Use Reserved, not to be assigned. This range is for sub-TLVs that can be silently dropped if not recognized. 64512-65535 First Come First Served This range is for sub-TLVs that can be silently dropped if not recognized. 0 Reserved 1 LDP IPv4 prefix 2 LDP IPv6 prefix 3 RSVP IPv4 LSP 4 RSVP IPv6 LSP 5 Unassigned 6 VPN IPv4 prefix 7 VPN IPv6 prefix 8 L2 VPN endpoint 9 "FEC 128" Pseudowire - IPv4 DEPRECATED 10 "FEC 128" Pseudowire - IPv4 11 "FEC 129" Pseudowire - IPv4 12 BGP labeled IPv4 prefix 13 BGP labeled IPv6 prefix 14 Generic IPv4 prefix 15 Generic IPv6 prefix 16 Nil FEC 17 RSVP P2MP IPv4 Session 18 RSVP P2MP IPv6 Session 19 Multicast P2MP LDP FEC Stack 20 Multicast MP2MP LDP FEC Stack 21 Unassigned 22 Static LSP 23 Static Pseudowire 24 "FEC 128" Pseudowire - IPv6 25 "FEC 129" Pseudowire - IPv6 26 IPv4 RSVP Tunnel 27 IPv6 RSVP Tunnel 28 Static Tunnel 29 HSMP-upstream LDP FEC Stack 30 HSMP-downstream LDP FEC Stack 31 MT LDP IPv4 prefix 32 MT LDP IPv6 prefix 33 Entropy label FEC 34 IPv4 IGP-Prefix Segment ID RFC8287, Section 5.1 35 IPv6 IGP-Prefix Segment ID RFC8287, Section 5.2 36 IGP-Adjacency Segment ID RFC8287, Section 5.3 37 P2MP Pseudowire sub-TLV 38 PeerAdj SID 39 PeerNode SID 40 PeerSet SID 41 SR MPLS P2MP Policy Tree Instance 42 EVPN MAC/IP 43 EVPN Inclusive Multicast 44 EVPN Ethernet Auto-Discovery 45 EVPN IP Prefix 46 SID only, in the form of MPLS label RFC9716, Section 4.1 47 IPv4 Node Address with an optional SID for SR-MPLS RFC9716, Section 4.2 48 IPv6 Node Address with an optional SID for SR-MPLS RFC9716, Section 4.3 49 SR Policy Associated PSID - IPv4 RFC9884, Section 3.1 50 SR Candidate Path Associated PSID - IPv4 RFC9884, Section 3.2 51 SR Segment List Associated PSID - IPv4 RFC9884, Section 3.3 52 SR Policy Associated PSID - IPv6 RFC9884, Section 3.4 53 SR Candidate Path Associated PSID - IPv6 RFC9884, Section 3.5 54 SR Segment List Associated PSID - IPv6 RFC9884, Section 3.6 55-31739 Unassigned 31740-31743 Reserved for Experimental Use Not to be assigned. This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744 IPv4 BGP Classful Transport 31745 IPv6 BGP Classful Transport 31746-64507 Unassigned 64508-64511 Reserved for Experimental Use Not to be assigned. This range is for sub-TLVs that can be silently dropped if not recognized. 64512-65535 Unassigned 0-16383 Standards Action This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 16384-31739 RFC Required This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31740-31743 Experimental Use Reserved, not to be assigned. This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744-32767 First Come First Served This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 32768-49161 Standards Action This range is for sub-TLVs that can be silently dropped if not recognized. 49162-64507 RFC Required This range is for sub-TLVs that can be silently dropped if not recognized. 64508-64511 Experimental Use Reserved, not to be assigned. This range is for sub-TLVs that can be silently dropped if not recognized. 64512-65535 First Come First Served This range is for sub-TLVs that can be silently dropped if not recognized. 0 Reserved 1 Incoming Label Stack 2 Incoming Interface Index 3-31739 Unassigned 31740-31743 Reserved for Experimental Use Not to be assigned. This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744-64507 Unassigned 64508-64511 Reserved for Experimental Use Not to be assigned. This range is for sub-TLVs that can be silently dropped if not recognized. 64512-65535 Unassigned None Any value TLV Not Understood The entire errored TLV is returned 0-16383 Standards Action This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 16384-31739 RFC Required This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31740-31743 Experimental Use Reserved, not to be assigned. This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744-32767 First Come First Served This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 32768-49161 Standards Action This range is for sub-TLVs that can be silently dropped if not recognized. 49162-64507 RFC Required This range is for sub-TLVs that can be silently dropped if not recognized. 64508-64511 Experimental Use Reserved, not to be assigned. This range is for sub-TLVs that can be silently dropped if not recognized. 64512-65535 First Come First Served This range is for sub-TLVs that can be silently dropped if not recognized. 0 Reserved 1 IPv4 Egress Address P2MP Responder 2 IPv6 Egress Address P2MP Responder 3 IPv4 Node Address P2MP Responder 4 IPv6 Node Address P2MP Responder 5-31739 Unassigned 31740-31743 Reserved for Experimental Use Not to be assigned. This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744-64507 Unassigned 64508-64511 Reserved for Experimental Use Not to be assigned. This range is for sub-TLVs that can be silently dropped if not recognized. 64512-65535 Unassigned 0-16383 Standards Action This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 16384-31739 RFC Required This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31740-31743 Experimental Use Reserved, not to be assigned. This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744-32767 First Come First Served This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 32768-49161 Standards Action This range is for sub-TLVs that can be silently dropped if not recognized. 49162-64507 RFC Required This range is for sub-TLVs that can be silently dropped if not recognized. 64508-64511 Experimental Use Reserved, not to be assigned. This range is for sub-TLVs that can be silently dropped if not recognized. 64512-65535 First Come First Served This range is for sub-TLVs that can be silently dropped if not recognized. 0 Reserved 1 Multipath data 2 Label stack 3 FEC stack change 4 Local Interface Index 5 Remote Interface Index 6-31739 Unassigned 31740-31743 Reserved for Experimental Use Not to be assigned. This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744-64507 Unassigned 64508-64511 Reserved for Experimental Use Not to be assigned. This range is for sub-TLVs that can be silently dropped if not recognized. 64512-65535 Unassigned 0-16383 Standards Action This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 16384-31739 RFC Required This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31740-31743 Experimental Use Reserved, not to be assigned. This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744-32767 First Come First Served This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 32768-49161 Standards Action This range is for sub-TLVs that can be silently dropped if not recognized. 49162-64507 RFC Required This range is for sub-TLVs that can be silently dropped if not recognized. 64508-64511 Experimental Use Reserved, not to be assigned. This range is for sub-TLVs that can be silently dropped if not recognized. 64512-65535 First Come First Served This range is for sub-TLVs that can be silently dropped if not recognized. 0 Reserved 1 Next Hop 2-31739 Unassigned 31740-31743 Reserved for Experimental Use Not to be assigned. This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744-64507 Unassigned 64508-64511 Reserved for Experimental Use Not to be assigned. This range is for sub-TLVs that can be silently dropped if not recognized. 64512-65535 Unassigned 0-16383 Standards Action This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 16384-31739 RFC Required This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31740-31743 Experimental Use Reserved, not to be assigned. This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744-32767 First Come First Served This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 32768-49161 Standards Action This range is for sub-TLVs that can be silently dropped if not recognized. 49162-64507 RFC Required This range is for sub-TLVs that can be silently dropped if not recognized. 64508-64511 Experimental Use Reserved, not to be assigned. This range is for sub-TLVs that can be silently dropped if not recognized. 64512-65535 First Come First Served This range is for sub-TLVs that can be silently dropped if not recognized. 0 Reserved 1-99 Unassigned 100 BFD Configuration 101 BFD Local Discriminator 102 BFD Negotiation Timer Parameters 103 BFD Authentication 104 Traffic Class 105-199 Unassigned 200 Performance Monitoring 201 PM Loss Measurement 202 PM Delay Measurement 203-299 Unassigned 300 Fault Management Signal 301-399 Unassigned 400 Source MEP-ID 401-31739 Unassigned 31740-31743 Reserved for Experimental Use Not to be assigned. This range is for sub-TLVs that require an error message if not recognized. RFC9041, Section 3.1 31744-64507 Unassigned 64508-64511 Reserved for Experimental Use Not to be assigned. This range is for sub-TLVs that can be silently dropped if not recognized. 64512-65535 Unassigned Moved to per . Moved to per . Moved to per . Moved to per . Standards Action 15 V Flag 14 T Flag 13 Validate Reverse Path 12-0 Unassigned Standards Action When a code point is assigned that is not also assigned in the Next Hop Address Type Registry, the code point there must be marked "Reserved". 0 Unassigned 1 IPv4 Numbered 16 2 IPv4 Unnumbered 16 3 IPv6 Numbered 40 4 IPv6 Unnumbered 28 5 Non IP 12 6 Reserved 7 Reserved 8-255 Unassigned Standards Action When a code point is assigned that is not also assigned in the Downstream Mapping Address Type Registry, the code point there must be marked "Reserved". 0 Unassigned 1 IPv4 Numbered 4 4 2 IPv4 Unnumbered 4 4 3 IPv6 Numbered 16 16 4 IPv6 Unnumbered 16 4 5 Reserved 6 IPv4 Protocol Adj 4 0 7 IPv6 Protocol Adj 16 0 8-255 Unassigned 0x0000-0xFFFB Standards Action 0xFFFC-0xFFFF Experimental Use 0x0000 No return code 0x0001 Malformed Reply Path TLV was received 0x0002 One or more of the sub-TLVs in the Reply Path TLV were not understood 0x0003 The echo reply was sent successfully using the specified Reply Path 0x0004 The specified Reply Path was not found, the echo reply was sent via other LSP 0x0005 The specified Reply Path was not found, the echo reply was sent via pure IP forwarding (non-MPLS) path 0x0006 Use Reply Path TLV from this echo reply for building the next echo request 0x0007 Local policy does not allow dynamic return path building 0x0008-0xFFFB Unassigned 0xFFFC-0xFFFF Reserved for Experimental Use Standards Action 7 N: Treat as a Non-IP Packet 6 I: Interface and Label Stack Object Request 5 E: ELI/EL push indicator 4 L: Label-based load balance indicator 3 G: LAG Description Indicator 2-0 Unassigned Standards Action 0-250 Standards Action 251-254 Experimental Use 0 no multipath 1 Unassigned 2 IP address 3 Unassigned 4 IP address range 5-7 Unassigned 8 Bit-masked IP address set 9 Bit-masked label set 10 IP and label set 11-250 Unassigned 251-254 Reserved for Experimental Use 255 Reserved 1-250 Standards Action 251-254 Experimental Use 0 Reserved 1 Drop Pad TLV from reply 2 Copy Pad TLV to reply 3-250 Unassigned 251-254 Reserved for Experimental Use 255 Reserved 1-250 Standards Action 251-254 Experimental Use 0 Reserved 1 IPv4 Numbered 2 IPv4 Unnumbered 3 IPv6 Numbered 4 IPv6 Unnumbered 5-250 Unassigned 251-254 Reserved for Experimental Use 255 Reserved Standards Action 0 Request for FEC Neighbor Address info 1 Request for Downstream Mapping 2 Request for Downstream Detailed Mapping 3 Explicit DSCP Request 4-15 Unassigned Standards Action 0 C Continuity Check (CC) 1 V Connectivity Verification (CV) 2 F Fault Management Signal (FMS) 3 L Performance Monitoring/Loss (PM/Loss) 4 D Performance Monitoring/Delay (PM/Delay) 5 T Throughput Measurement 6-30 Unassigned (Must be zero) 31 Reserved 0-250 Standards Action 251-254 Experimental Use 0 Any IGP Protocol 1 OSPF To be used for OSPFv2 only. 2 ISIS 3 OSPFv3 4-250 Unassigned 251-254 Reserved for Experimental Use 255 Reserved 0-250 Standards Action 251-254 Experimental Use 0 Unnumbered interface Adjacency 1 Parallel Adjacency 2-3 Unassigned 4 IPv4, non-parallel Adjacency 5 Unassigned 6 IPv4, non-parallel Adjacency 7-250 Unassigned 251-254 Reserved for Experimental Use 255 Reserved 0-250 Standards Action 251-254 Experimental Use 0 Unknown RFC8029, Section 3.4.1.2 1 Static RFC8029, Section 3.4.1.2 2 BGP RFC8029, Section 3.4.1.2 3 LDP RFC8029, Section 3.4.1.2 4 RSVP-TE RFC8029, Section 3.4.1.2 5 OSPF RFC8287, Section 6 To be used for OSPFv2 only. 6 ISIS RFC8287, Section 6 7 OSPFv3 8-250 Unassigned 251-254 Reserved for Experimental Use 255 Reserved Standards Action 31 D: Downstream LAG Info Accommodation 30 U: Upstream LAG Info Accommodation 0-29 Unassigned Standards Action 15 M: LAG Member Link Indicator 0-14 Unassigned Standards Action 0 Unassigned 1 A-Flag RFC9716, Section 4.4 2-7 Unassigned