Class,Description,Reference
0,Null Class,[RFC1990]
1,Locally Assigned,[RFC1990]
2,Internet Protocol (IPv4),[RFC1990]
3,IEEE 802.1 global MAC address,[RFC1990]
4,PPP Magic Number Block,[RFC1990]
5,Public Switched Network Director Number,[RFC1990]
6,Internet Protocol (Ipv6) Address,[RFC3790]