We have a Digium PBX and two gateways behind an Atlas 550. We've been having problems with lack of sound on outbound calls, and Digium support recommended we make sure that SIP ALG is not enabled on our firewall. I've poked around the menus on the 550 but haven't been able to find any reference to SIP ALG. Is this a feature on the 550, and if so where can I confirm that it's disabled?
The SIP ALG is for "IP Devices" and routers. The ATLAS does not have a SIP ALG and should not be used as a router, even though it does have some routing capabilities.
If you are only using the ATLAS DIAL PLAN and/or DEDICATED MAP, then it is strictly TDM and there is no SIP involved with the traffic through the ATLAS.
Hope this makes sense,