/usr/bin/iptunnel

Usage: iptunnel { add | change | del | show } [ NAME ]
          [ mode { ipip | gre | sit } ] [ remote ADDR ] [ local ADDR ]
          [ [i|o]seq ] [ [i|o]key KEY ] [ [i|o]csum ]
          [ ttl TTL ] [ tos TOS ] [ nopmtudisc ] [ dev PHYS_DEV ]
       iptunnel -V | --version

Where: NAME := STRING
       ADDR := { IP_ADDRESS | any }
       TOS  := { NUMBER | inherit }
       TTL  := { 1..255 | inherit }
       KEY  := { DOTTED_QUAD | NUMBER }