C-Type,Description,Reference
0,Reserved,
1,IPv4 LOCAL_LINK_ID,[RFC4204]
2,IPv4 REMOTE_LINK_ID,[RFC4204]
3,IPv6 LOCAL_LINK_ID,[RFC4204]
4,IPv6 REMOTE_LINK_ID,[RFC4204]
5,Unnumbered LOCAL_LINK_ID,[RFC4204]
6,Unnumbered REMOTE_LINK_ID,[RFC4204]
7-119,Unassigned,
120-127,Private Use,[RFC4204]