/etc/protocolsを参照するとシステムに定義されているプロトコルの番号を調べることができます。
# cat /etc/protocols # /etc/protocols: # $Id: protocols,v 1.5 2006/10/11 15:39:11 pknirsch Exp $ # # Internet (IP) protocols # # from: @(#)protocols 5.1 (Berkeley) 4/17/89 # # Updated for NetBSD based on RFC 1340, Assigned Numbers (July 1992). # # See also http://www.iana.org/assignments/protocol-numbers ip 0 IP # internet protocol, pseudo protocol number hopopt 0 HOPOPT # hop-by-hop options for ipv6 icmp 1 ICMP # internet control message protocol igmp 2 IGMP # internet group management protocol ggp 3 GGP # gateway-gateway protocol ipencap 4 IP-ENCAP # IP encapsulated in IP (officially ``IP'') st 5 ST # ST datagram mode tcp 6 TCP # transmission control protocol cbt 7 CBT # CBT, Tony Ballardie <A.Ballardie@cs.ucl.ac.uk> egp 8 EGP # exterior gateway protocol igp 9 IGP # any private interior gateway (Cisco: for IGRP) bbn-rcc 10 BBN-RCC-MON # BBN RCC Monitoring nvp 11 NVP-II # Network Voice Protocol ・・・