| 0 | HOPOPT | IPv6 Hop-by-Hop Option | RFC 8200 |
| 1 | ICMP | Internet Control Message Protocol | RFC 792 |
| 2 | IGMP | Internet Group Management Protocol | RFC 1112 |
| 3 | GGP | Gateway-to-Gateway Protocol | RFC 823 |
| 4 | IP-in-IP | IP in IP (encapsulation) | RFC 2003 |
| 5 | ST | Internet Stream Protocol | RFC 1190, RFC 1819 |
| 6 | TCP | Transmission Control Protocol | RFC 793 |
| 7 | CBT | Core-based trees | RFC 2189 |
| 8 | EGP | Exterior Gateway Protocol | RFC 888 |
| 9 | IGP | Interior Gateway Protocol (any private interior gateway (used by Cisco for their IGRP)) | |
| 10 | BBN-RCC-MON | BBN RCC Monitoring | |
| 11 | NVP-II | Network Voice Protocol | RFC 741 |
| 12 | PUP | Xerox PUP | |
| 13 | ARGUS | ARGUS | |
| 14 | EMCON | EMCON | |
| 15 | XNET | Cross Net Debugger | IEN 158[2] |
| 16 | CHAOS | Chaos | |
| 17 | UDP | User Datagram Protocol | RFC 768 |
| 18 | MUX | Multiplexing | IEN 90[3] |
| 19 | DCN-MEAS | DCN Measurement Subsystems | |
| 20 | HMP | Host Monitoring Protocol | RFC 869 |
| 21 | PRM | Packet Radio Measurement | |
| 22 | XNS-IDP | XEROX NS IDP | |
| 23 | TRUNK-1 | Trunk-1 | |
| 24 | TRUNK-2 | Trunk-2 | |
| 25 | LEAF-1 | Leaf-1 | |
| 26 | LEAF-2 | Leaf-2 | |
| 27 | RDP | Reliable Data Protocol | RFC 908 |
| 28 | IRTP | Internet Reliable Transaction Protocol | RFC 938 |
| 29 | ISO-TP4 | ISO Transport Protocol Class 4 | RFC 905 |
| 30 | NETBLT | Bulk Data Transfer Protocol | RFC 998 |
| 31 | MFE-NSP | MFE Network Services Protocol | |
| 32 | MERIT-INP | MERIT Internodal Protocol | |
| 33 | DCCP | Datagram Congestion Control Protocol | RFC 4340 |
| 34 | 3PC | Third Party Connect Protocol | |
| 35 | IDPR | Inter-Domain Policy Routing Protocol | RFC 1479 |
| 36 | XTP | Xpress Transport Protocol | |
| 37 | DDP | Datagram Delivery Protocol | |
| 38 | IDPR-CMTP | IDPR Control Message Transport Protocol | |
| 39 | TP++ | TP++ Transport Protocol | |
| 40 | IL | IL Transport Protocol | |
| 41 | IPv6 | IPv6 Encapsulation | RFC 2473 |
| 42 | SDRP | Source Demand Routing Protocol | RFC 1940 |
| 43 | IPv6-Route | Routing Header for IPv6 | RFC 8200 |
| 44 | IPv6-Frag | Fragment Header for IPv6 | RFC 8200 |
| 45 | IDRP | Inter-Domain Routing Protocol | |
| 46 | RSVP | Resource Reservation Protocol | RFC 2205 |
| 47 | GREs | Generic Routing Encapsulation | RFC 2784, RFC 2890 |
| 48 | DSR | Dynamic Source Routing Protocol | RFC 4728 |
| 49 | BNA | Burroughs Network Architecture | |
| 50 | ESP | Encapsulating Security Payload | RFC 4303 |
| 51 | AH | Authentication Header | RFC 4302 |
| 52 | I-NLSP | Integrated Net Layer Security Protocol | TUBA |
| 53 | SwIPe | SwIPe | RFC 5237 |
| 54 | NARP | NBMA Address Resolution Protocol | RFC 1735 |
| 55 | MOBILE | IP Mobility (Min Encap) | RFC 2004 |
| 56 | TLSP | Transport Layer Security Protocol (using Kryptonet key management) | |
| 57 | SKIP | Simple Key-Management for Internet Protocol | RFC 2356 |
| 58 | IPv6-ICMP | ICMP for IPv6 | RFC 4443, RFC 4884 |
| 59 | IPv6-NoNxt | No Next Header for IPv6 | RFC 8200 |
| 60 | IPv6-Opts | Destination Options for IPv6 | RFC 8200 |
| 61 | Any host internal protocol | ||
| 62 | CFTP | CFTP | |
| 63 | Any local network | ||
| SAT-EXPAK | SATNET and Backroom EXPAK | ||
| 65 | KRYPTOLAN | Kryptolan | |
| 66 | RVD | MIT Remote Virtual Disk Protocol | |
| 67 | IPPC | Internet Pluribus Packet Core | |
| 68 | Any distributed file system | ||
| 69 | SAT-MON | SATNET Monitoring | |
| 70 | VISA | VISA Protocol | |
| 71 | IPCU | Internet Packet Core Utility | |
| 72 | CPNX | Computer Protocol Network Executive | |
| 73 | CPHB | Computer Protocol Heart Beat | |
| 74 | WSN | Wang Span Network | |
| 75 | PVP | Packet Video Protocol | |
| 76 | BR-SAT-MON | Backroom SATNET Monitoring | |
| 77 | SUN-ND | SUN ND PROTOCOL-Temporary | |
| 78 | WB-MON | WIDEBAND Monitoring | |
| 79 | WB-EXPAK | WIDEBAND EXPAK | |
| 80 | ISO-IP | International Organization for Standardization Internet Protocol | |
| 81 | VMTP | Versatile Message Transaction Protocol | RFC 1045 |
| 82 | SECURE-VMTP | Secure Versatile Message Transaction Protocol | RFC 1045 |
| 83 | VINES | VINES | |
| 84 | TTP | TTP | |
| 84 | IPTM | Internet Protocol Traffic Manager | |
| 85 | NSFNET-IGP | NSFNET-IGP | |
| 86 | DGP | Dissimilar Gateway Protocol | |
| 87 | TCF | TCF | |
| 88 | EIGRP | EIGRP | Informational RFC 7868 |
| 89 | OSPF | Open Shortest Path First | RFC 2328 |
| 90 | Sprite-RPC | Sprite RPC Protocol | |
| 91 | LARP | Locus Address Resolution Protocol | |
| 92 | MTP | Multicast Transport Protocol | |
| 93 | AX.25 | AX.25 | |
| 94 | OS | KA9Q NOS compatible IP over IP tunneling | |
| 95 | MICP | Mobile Internetworking Control Protocol | |
| 96 | SCC-SP | Semaphore Communications Sec. Pro | |
| 97 | ETHERIP | Ethernet-within-IP Encapsulation | RFC 3378 |
| 98 | ENCAP | Encapsulation Header | RFC 1241 |
| 99 | Any private encryption scheme | ||
| 100 | GMTP | GMTP | |
| 101 | IFMP | Ipsilon Flow Management Protocol | |
| 102 | PNNI | PNNI over IP | |
| 103 | PIM | Protocol Independent Multicast | |
| 104 | ARIS | IBM’s ARIS (Aggregate Route IP Switching) Protocol | |
| 105 | SCPS | SCPS (Space Communications Protocol Standards) | SCPS-TP[4] |
| 106 | QNX | QNX | |
| 107 | A/N | Active Networks | |
| 108 | IPComp | IP Payload Compression Protocol | RFC 3173 |
| 109 | SNP | Sitara Networks Protocol | |
| 110 | Compaq-Peer | Compaq Peer Protocol | |
| 111 | IPX-in-IP | IPX in IP | |
| 112 | VRRP | Virtual Router Redundancy Protocol, Common Address Redundancy Protocol (not IANA assigned) | VRRP:RFC 3768 |
| 113 | PGM | PGM Reliable Transport Protocol | RFC 3208 |
| 114 | Any 0-hop protocol | ||
| 115 | L2TP | Layer Two Tunneling Protocol Version 3 | RFC 3931 |
| 116 | DDX | D-II Data Exchange (DDX) | |
| 117 | IATP | Interactive Agent Transfer Protocol | |
| 118 | STP | Schedule Transfer Protocol | |
| 119 | SRP | SpectraLink Radio Protocol | |
| 120 | UTI | Universal Transport Interface Protocol | |
| 121 | SMP | Simple Message Protocol | |
| 122 | SM | Simple Multicast Protocol | draft-perlman-simple-multicast-03 |
| 123 | PTP | Performance Transparency Protocol | |
| 124 | IS-IS over IPv4 | Intermediate System to Intermediate System (IS-IS) Protocol over IPv4 | RFC 1142 and RFC 1195 |
| 125 | FIRE | Flexible Intra-AS Routing Environment | |
| 126 | CRTP | Combat Radio Transport Protocol | |
| 127 | CRUDP | Combat Radio User Datagram | |
| 128 | SSCOPMCE | Service-Specific Connection-Oriented Protocol in a Multilink and Connectionless Environment | ITU-T Q.2111 (1999) |
| 129 | IPLT | ||
| 130 | SPS | Secure Packet Shield | |
| 131 | PIPE | Private IP Encapsulation within IP | Expired I-D draft-petri-mobileip-pipe-00.txt |
| 132 | SCTP | Stream Control Transmission Protocol | RFC 4960 |
| 133 | FC | Fibre Channel | |
| 134 | RSVP-E2E-IGNORE | Reservation Protocol (RSVP) End-to-End Ignore | RFC 3175 |
| 135 | Mobility Header | Mobility Extension Header for IPv6 | RFC 6275 |
| 136 | UDPLite | Lightweight User Datagram Protocol | RFC 3828 |
| 137 | MPLS-in-IP | Multiprotocol Label Switching Encapsulated in IP | RFC 4023, RFC 5332 |
| 138 | manet | MANET Protocols | RFC 5498 |
| 139 | HIP | Host Identity Protocol | RFC 5201 |
| 140 | Shim6 | Site Multihoming by IPv6 Intermediation | RFC 5533 |
| 141 | WESP | Wrapped Encapsulating Security Payload | RFC 5840 |
| 142 | ROHC | Robust Header Compression | RFC 5856 |
| 143 | Ethernet | IPv6 Segment Routing (TEMPORARY – registered 2020-01-31, expires 2021-01-31) | |
| 144-252 | Unassigned | ||
| 253-254 | Use for experimentation and testing | RFC 3692 | |