I'm having an issue with about 10% of my ougoing calls with Q931 issuing a release_complete message right after I send a SETUP message. Cause code is 0x80A2: no circuit/channel available. Checking with show idsn status I can see that there are plenty of available circuits (also DSPs are available). The fact that we can see a 0x80 in the cause code tells me that it's the router who is unable to get a circuit. The gateway is a 2821 running 12.4(6)T software.
As most calls go through, I suspect that it isn't a configuration issue. The call will succeed after a second attempt.
I have the feeling it might be linked to the fact that we are spoofing the interface. Could it be that layer 2 of the signaling channel doesn't get enough time to come up in order to deal with the request?
Any help or directions would be greatly appreciated.