I have a Cisco 2811 (IOS: 12.4(3g)) on which I do some SIP application development. The device is set up as an ISDN-SIP gateway.
The issue is that if I let the outgoing call to ring for more than about 20 sec, the gateway responds with 504 Gateway Timeout and disconnects the call. The call is triggered by a SIP INVITE that I generate and everything works fine if I answer the call earlier than this timeout. I checked the logs and there is no ISDN or SIP event that triggers the 504 Gateway Timeout - it seemingly comes out of nowhere.
Do you have any idea what can cause this timeout? Do you have any advice how I can obtain more information about the cause (e.g. more logging?)