SIP VOIP across 5510 ASA not functional

[mmcgeehan@anazaohealth.com]

Have been trying to get VOIP service (BroadVoice) working across our Cisco 5510 to our Avaya phone system for a while. We were told all we need do is open the appropriate ports to the Avaya control unit and set up 1 to 1 Nat from the public IP of the ASA (one of them actually) to the Avaya control unit. This has been done.

We get outbound working with Voice in one direction. If we turn on SIP inspection we get outbound with Voice in both directions. However, in either configuration, No inbound calling works. We can see the traffic hit the phone system and get SIP 404 errors. With SIP inspection on, the private IP is referenced, with it turned off the public IP is referenced in the SIP header(phone#@IPaddress). Also, we have turned SIP inspection off, as having it turned on doubles the CPU usage on the appliance and it causes bizarre things to happen with HTTP traffic. (we have 2 internal webservers). Any suggestions? 

[Mohammed al Baqari]

If inspection used asa ip will referenced in the message. It seems that
your sip trunk is pointed to ip different from the one in sip message

[mmcgeehan@anazaohealth.com]

SIP provider is pointed to the public IP of the ASA. With SIP inspection turned on this gets properly re-written to the private IP of the Avaya Control Unit. With SIP inspection turned off, the IP remains the public IP of the ASA. 

I suspect there is some subtlety to the NAT that I'm  missing. It's just set up as object 1 to 1 NAT, for UDP 5060.