Symptom

NAT ALG is translating the Call-ID within the SIP Message Header, causing calls to fail. SIP INVITE inbound is getting translated properly. SIP 180 Ringing packet is getting the Call-ID altered by the NAT ALG outbound. When the initiator of the SIP call receives the 180 Ringing with a different Call-ID it doesn't recognize the packet and the call fails.

Conditions

1. NAT ALG is used for SIP traffic. 2. Calls are originated from the WAN. 3. Configuration is as shown: interface ip nat outside ip nat inside source list nat-dia-vpn-hop-list interface overload ip nat inside source static vrf egress-interface ip nat service all-algs ip nat service sip tcp port 5060 ip nat service sip udp port 5060

Workaround

At this time there is no workaround. Please open a TAC case.

Further Problem Description