AT&T Services, Inc. ATT (NET-12-0-0-0-1) 12.0.0.0 - 12.255.255.255 AT&T Services, Inc. ATTWORLD25 (NET-12-203-0-0-1) 12.203.0.0 - 12.203.255.255 MC MASTER CARR MC-MASTE34-197 (NET-12-203-197-0-1) 12.203.197.0 - 12.203.197.255