192.20.0.0 - 192.20.224.0 AT&T Bell Laboratories (NETBLK-ATT-MD-NET2) 192.20.110.0 AT&T Bell Laboratories (NET-ATT-HADLEY-1) 192.20.115.0 AT&T Bell Laboratories (NET-ATT-HADLEY-2) 192.20.225.0 AT&T Laboratories (NET-MH-INTER-NET) 192.20.226.0 - 192.20.238.0 AT&T Bell Laboratories (NETBLK-ATT-MD-NET3) 192.20.239.0 AT&T Bell Laboratories (NET- ATT-MD-NET) 192.20.240.0 - 192.20.255.0 AT&T Bell Laboratories (NETBLK-ATT-MD-NET4)