I noticed when my Cisco device sends a SUBSCRIBE message to Asterisk for voice mail subscription. The Asterisk server will send the wrong call ID back. Thus, the Cisco sends a 481 back to the Asterisk. I believe the below section in RFC 3265 is relevant: 3.3.4 NOTIFY requests are matched to such SUBSCRIBE requests if they contain the same "Call-ID", a "To" header "tag" parameter which matches the "From" header "tag" parameter of the SUBSCRIBE, and the same "Event" header field. Rules for comparisons of the "Event" headers are described in section 7.2.1. If a matching NOTIFY request contains a "Subscription-State" of "active" or "pending", it creates a new subscription and a new dialog (unless they have already been created by a matching response, as described above). Below is a portion of the trap I obtained from the Asterisk Server. A complete trap can be found at http://www.pasewaldt.com/notify.html Sip read: SUBSCRIBE sip:2486@192.168.0.100:5060 SIP/2.0 Via: SIP/2.0/UDP 192.168.0.1:5060;branch=z9hG4bKFC2 From: "2486" <sip:2486@192.168.0.1>;tag=6C30-149 To: <sip:2486@192.168.0.100> Date: Call-ID: 2C1ED0F6-2BDE11D6-80048294-A080CC2F CSeq: 101 SUBSCRIBE Timestamp: 1089723760 Contact: <sip:2486@192.168.0.1:5060> Event: message-summary Expires: 600 Accept: application/simple-message-summary Content-Length: 0 13 headers, 0 lines ^Dasterick*CLI> Using latest SUBSCRIBE request as basis request Sending to 192.168.0.1 : 5060 (non-NAT) Looking for 2486 in voice-mail Reliably Transmitting: NOTIFY sip:2486@192.168.0.1 SIP/2.0 Via: SIP/2.0/UDP 192.168.0.100:5060;branch=z9hG4bK19c0b453 From: "asterisk" <sip:asterisk@192.168.0.100>;tag=as288443e6 To: <sip:2486@192.168.0.1> Contact: <sip:asterisk@192.168.0.100> Call-ID: 57f3d594208235d27e796fd27db42c1b@192.168.0.100 CSeq: 102 NOTIFY User-Agent: Asterisk PBX Event: message-summary Content-Type: application/simple-message-summary Content-Length: 37 Messages-Waiting: yes Voicemail: 7/0 (no NAT) to 192.168.0 Kurt __________________________________ Do you Yahoo!? Yahoo! Mail - 50x more storage than other providers! http://promotions.yahoo.com/new_mail