| Protocol | Description |
| ip | internet protocol, pseudo protocol number |
| icmp | internet control message protocol |
| igmp | Internet Group Management |
| ggp | gateway-gateway protocol |
| ipencap | IP encapsulated in IP (officially ``IP'') |
| st | ST datagram mod |
| tcp | transmission control protocol |
| egp | exterior gateway protocol |
| igp | any private interior gateway (Cisco) |
| pup | PARC universal packet protocol |
| udp | user datagram protocol |
| hmp | host monitoring protocol |
| xns-idp | Xerox NS IDP |
| rdp | reliable datagram protocol |
| iso-tp4 | ISO Transport Protocol class 4 [RFC905] |
| xtp | Xpress Transfer Protocol |
| ddp | Datagram Delivery Protocol |
| idpr-cmtp | IDPR Control Message Transport |
| ipv6 | Internet Protocol, version 6 |
| ipv6-route | Routing Header for IPv6 |
| ipv6-frag | Fragment Header for IPv6 |
| idrp | Inter-Domain Routing Protocol |
| rsvp | Reservation Protocol |
| gre | General Routing Encapsulation |
| esp | Encap Security Payload [RFC2406] |
| ah | Authentication Header [RFC2402] |
| skip | SKIP |
| ipv6-icmp | ICMP for IPv6 |
| ipv6-nonxt | No Next Header for IPv6 |
| ipv6-opts | Destination Options for IPv6 |
| rspf | Radio Shortest Path First (officially CPHB) |
| vmtp | Versatile Message Transport |
| eigrp | Enhanced Interior Routing Protocol (Cisco) |
| ospf | Open Shortest Path First IGP |
| ax25 | AX.25 frames |
| ipip | IP-within-IP Encapsulation Protocol |
| etherip | Ethernet-within-IP Encapsulation [RFC3378] |
| encap | Yet Another IP encapsulation [RFC1241] |
| pim | Protocol Independent Multicast |
| ipcomp | IP Payload Compression Protocol |
| vrrp | Virtual Router Redundancy Protocol |
| l2tp | Layer Two Tunneling Protocol [RFC2661] |
| isis | IS-IS over IPv4 |
| sctp | Stream Control Transmission Protocol |
| fc | Fibre Channel |
