2025-12-24 This registry has been closed in favor of the IPv6 Extension Header Types registry, also located at . Standards Action or IESG Approval The "IPv6 Extension Header" field in the Assigned Internet Protocol Numbers registry at should be updated for any Protocol Number added to this registry. When a new code is assigned to an IPv6 Extension Header, the next available free bit in IPFIX ipv6ExtensionHeaders Bits is selected for this new Extension Header. IPFIX ipv6ExtensionHeaders Bits is updated accordingly. Modifications to existing registrations must be mirrored in IPFIX ipv6ExtensionHeaders Bits. When this registry is modified, the YANG module "iana-ipv6-ext-types" must be updated as defined in . 0 IPv6 Hop-by-Hop Option 43 Routing Header for IPv6 44 Fragment Header for IPv6 50 Encapsulating Security Payload 51 Authentication Header 60 Destination Options for IPv6 135 Mobility Header 139 Host Identity Protocol 140 Shim6 Protocol 253 Use for experimentation and testing 254 Use for experimentation and testing IESG Approval, IETF Review or Standards Action From IPv6 Option Types are 8-bit values, structured as three subfields, are defined in Section 4.2 of . Each distinct 8-bit Option Type identifies a different option, i.e., the high-order 3 bits are considered part of the option identification. However, it is recommended that Option Types be assigned with distinct values in the "rest" subfield, until and unless that 5-bit space becomes full. 0x00 00 0 00000 Pad1 0x01 00 0 00001 PadN 0xC2 11 0 00010 Jumbo Payload 0x23 00 1 00011 RPL Option 0x63 01 1 00011 RPL Option (DEPRECATED) 0x04 00 0 00100 Tunnel Encapsulation Limit 0x05 00 0 00101 Router Alert (DEPRECATED for New Protocols) 0x26 00 1 00110 Quick-Start 0x07 00 0 00111 CALIPSO 0x08 00 0 01000 SMF_DPD 0xC9 11 0 01001 Home Address 0x8A 10 0 01010 Endpoint Identification (DEPRECATED) [CHARLES LYNN] 0x8B 10 0 01011 ILNP Nonce 0x8C 10 0 01100 Line-Identification Option 0x4D 01 0 01101 Deprecated 0x6D 01 1 01101 MPL Option 0xEE 11 1 01110 IP_DFF 0x0F 00 0 01111 Performance and Diagnostic Metrics (PDM) 0x30 00 1 10000 Minimum Path MTU Hop-by-Hop Option 0x11 00 0 10001 IOAM Destination Option and IOAM Hop-by-Hop Option 0x31 00 1 10001 IOAM Destination Option and IOAM Hop-by-Hop Option 0x12 00 0 10010 AltMark 10011-11101 Unassigned 0x1E 00 0 11110 RFC3692-style Experiment [1] 0x3E 00 1 11110 RFC3692-style Experiment [1] 0x5E 01 0 11110 RFC3692-style Experiment [1] 0x7E 01 1 11110 RFC3692-style Experiment [1] 0x9E 10 0 11110 RFC3692-style Experiment [1] 0xBE 10 1 11110 RFC3692-style Experiment [1] 0xDE 11 0 11110 RFC3692-style Experiment [1] 0xFE 11 1 11110 RFC3692-style Experiment [1] 11111 Unassigned It is only appropriate to use these values in explicitly-configured experiments; they MUST NOT be shipped as defaults in implementations. See for details. IETF Review or IESG Approval For Traffic Class related information, please see ,, and . For IPv6 Router Alert Option Values, please see: 0 Source Route (DEPRECATED) 1 Nimrod (DEPRECATED 2009-05-06) 2 Type 2 Routing Header 3 RPL Source Route Header 4 Segment Routing Header (SRH) 5 CRH-16 6 CRH-32 7-252 Unassigned 253 RFC3692-style Experiment 1 [2] 254 RFC3692-style Experiment 2 [2] 255 Reserved It is only appropriate to use these values in explicitly-configured experiments; they MUST NOT be shipped as defaults in implementations. See for details. IETF Review 0-254 Unassigned 255 Reserved IETF Review 0 NULL No TaggerId field is present 1 DEFAULT A TaggerId of non-specific context is present 2 IPv4 A TaggerId representing an IPv4 address is present 3 IPv6 A TaggerId representing an IPv6 address is present 4-7 Unassigned IETF Review 0-1 Unassigned 2 O-flag 3-7 Unassigned IETF Review 0-127: TLVs that do not change en route. 128-255: TLVs that may change en route. 0 Pad1 TLV 1 Reserved 2 Reserved 3 Reserved 4 PadN TLV 5 HMAC TLV 6 Reserved 7-123 Unassigned 124-126 Experimentation and Test 127 Reserved 128-251 Unassigned 252-254 Experimentation and Test 255 Reserved