Internet Assigned Numbers Authority • Domains • Protocols • Numbers • About Internet Protocol Version 6 (IPv6) Parameters Last Updated 2025-12-24 Available Formats [IMG] XML [IMG] HTML [IMG] TXT Registries Included Below • Next Header Types • IPv6 Extension Header Types • Destination Options and Hop-by-Hop Options • Routing Types • RPL-option-TLV • TaggerId Types • Segment Routing Header Flags • Segment Routing Header TLVs Next Header Types Reference [RFC 8200][RFC 2780][RFC 7045] Note This registry has been closed in favor of the IPv6 Extension Header Types registry, also located at [Internet Protocol Version 6 (IPv6) Parameters]. IPv6 Extension Header Types Registration Procedure(s) Standards Action or IESG Approval Reference [RFC 2780][RFC 5237][RFC 7045][RFC 9899] Note The "IPv6 Extension Header" field in the Assigned Internet Protocol Numbers registry at [Protocol Numbers] should be updated for any Protocol Number added to this registry. Note 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]. Note When this registry is modified, the YANG module "iana-ipv6-ext-types" [YANG Parameters] must be updated as defined in [RFC 9899]. Available Formats [IMG] CSV Protocol Number Description Reference 0 IPv6 Hop-by-Hop Option [RFC 8200] 43 Routing Header for IPv6 [RFC 8200]; [RFC 5095] 44 Fragment Header for IPv6 [RFC 8200] 50 Encapsulating Security Payload [RFC 4303] 51 Authentication Header [RFC 4302] 60 Destination Options for IPv6 [RFC 8200] 135 Mobility Header [RFC 6275] 139 Host Identity Protocol [RFC 7401] 140 Shim6 Protocol [RFC 5533] 253 Use for experimentation and testing [RFC 3692]; [RFC 4727] 254 Use for experimentation and testing [RFC 3692]; [RFC 4727] Destination Options and Hop-by-Hop Options Registration Procedure(s) IESG Approval, IETF Review or Standards Action Reference [RFC 8200][RFC 2780][RFC 9673] Note From [RFC 8200] IPv6 Option Types are 8-bit values, structured as three subfields, are defined in [Section 4.2 of RFC 8200]. 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. Available Formats [IMG] CSV Hex Value Binary Value Description Reference act chg rest 0x00 00 0 00000 Pad1 [RFC 2460] 0x01 00 0 00001 PadN [RFC 2460] 0xC2 11 0 00010 Jumbo Payload [RFC 2675] 0x23 00 1 00011 RPL Option [RFC 9008] 0x63 01 1 00011 RPL Option (DEPRECATED) [RFC 6553]; [RFC 9008] 0x04 00 0 00100 Tunnel Encapsulation Limit [RFC 2473] 0x05 00 0 00101 Router Alert (DEPRECATED for New Protocols) [RFC 2711]; [RFC 9805] 0x26 00 1 00110 Quick-Start [RFC 4782]; [RFC Errata 2034] 0x07 00 0 00111 CALIPSO [RFC 5570] 0x08 00 0 01000 SMF_DPD [RFC 6621] 0xC9 11 0 01001 Home Address [RFC 6275] 0x8A 10 0 01010 Endpoint Identification (DEPRECATED) [[CHARLES LYNN]] 0x8B 10 0 01011 ILNP Nonce [RFC 6744] 0x8C 10 0 01100 Line-Identification Option [RFC 6788] 0x4D 01 0 01101 Deprecated [RFC 7731] 0x6D 01 1 01101 MPL Option [RFC 7731] 0xEE 11 1 01110 IP_DFF [RFC 6971] 0x0F 00 0 01111 Performance and Diagnostic Metrics (PDM) [RFC 8250] 0x30 00 1 10000 Minimum Path MTU Hop-by-Hop Option [RFC 9268] 0x11 00 0 10001 IOAM Destination Option and IOAM Hop-by-Hop Option [RFC 9486] 0x31 00 1 10001 IOAM Destination Option and IOAM Hop-by-Hop Option [RFC 9486] 0x12 00 0 10010 AltMark [RFC 9343] 10011-11101 Unassigned 0x1E 00 0 11110 RFC3692-style Experiment [1] [RFC 4727] 0x3E 00 1 11110 RFC3692-style Experiment [1] [RFC 4727] 0x5E 01 0 11110 RFC3692-style Experiment [1] [RFC 4727] 0x7E 01 1 11110 RFC3692-style Experiment [1] [RFC 4727] 0x9E 10 0 11110 RFC3692-style Experiment [1] [RFC 4727] 0xBE 10 1 11110 RFC3692-style Experiment [1] [RFC 4727] 0xDE 11 0 11110 RFC3692-style Experiment [1] [RFC 4727] 0xFE 11 1 11110 RFC3692-style Experiment [1] [RFC 4727] 11111 Unassigned Routing Types Registration Procedure(s) IETF Review or IESG Approval Reference [RFC 8200][RFC 5871] Note For Traffic Class related information, please see [RFC 2474],[RFC 3168], and [Differentiated Services Field Codepoints (DSCP)]. For IPv6 Router Alert Option Values, please see: [IPv6 Router Alert Option Values] Available Formats [IMG] CSV Value Description Reference 0 Source Route (DEPRECATED) [RFC 2460]; [RFC 5095] 1 Nimrod (DEPRECATED 2009-05-06) 2 Type 2 Routing Header [RFC 6275] 3 RPL Source Route Header [RFC 6554] 4 Segment Routing Header (SRH) [RFC 8754] 5 CRH-16 [RFC 9631] 6 CRH-32 [RFC 9631] 7-252 Unassigned 253 RFC3692-style Experiment 1 [2] [RFC 4727] 254 RFC3692-style Experiment 2 [2] [RFC 4727] 255 Reserved RPL-option-TLV Registration Procedure(s) IETF Review Reference [RFC 6553] Available Formats [IMG] CSV Value Description Reference 0-254 Unassigned 255 Reserved [RFC 6553] TaggerId Types Registration Procedure(s) IETF Review Reference [RFC 6621] Available Formats [IMG] CSV Type Mnemonic Description Reference 0 NULL No TaggerId field is present [RFC 6621] 1 DEFAULT A TaggerId of non-specific context is present [RFC 6621] 2 IPv4 A TaggerId representing an IPv4 address is present [RFC 6621] 3 IPv6 A TaggerId representing an IPv6 address is present [RFC 6621] 4-7 Unassigned Segment Routing Header Flags Registration Procedure(s) IETF Review Reference [RFC 8754] Available Formats [IMG] CSV Bit Description Reference 0-1 Unassigned 2 O-flag [RFC 9259] 3-7 Unassigned Segment Routing Header TLVs Registration Procedure(s) IETF Review Reference [RFC 8754][RFC Errata 7081] Note * 0-127: TLVs that do not change en route. * 128-255: TLVs that may change en route. Available Formats [IMG] CSV Value Description Reference 0 Pad1 TLV [RFC 8754] 1 Reserved [RFC 8754] 2 Reserved [RFC 8754] 3 Reserved [RFC 8754] 4 PadN TLV [RFC 8754] 5 HMAC TLV [RFC 8754] 6 Reserved [RFC 8754] 7-123 Unassigned 124-126 Experimentation and Test [RFC 8754] 127 Reserved [RFC 8754] 128-251 Unassigned 252-254 Experimentation and Test [RFC 8754] 255 Reserved [RFC 8754] Footnotes [1] It is only appropriate to use these values in explicitly-configured experiments; they MUST NOT be shipped as defaults in implementations. See [RFC 3692] for details. [2] It is only appropriate to use these values in explicitly-configured experiments; they MUST NOT be shipped as defaults in implementations. See [RFC 3692] for details. Licensing Terms