PSTN calls drop over SIP trunk between two clusters

[jugalkansal90]

I have 2 clusters A and B connected over a SIP trunk, extension to extension calls between them are completely fine. But when a phone on either side is forwarded to PSTN, then calls don't complete.

If a phone on cluster B is forwarded to PSTN and gets call from cluster A, PSTN destination sees the call but it drops immediately after connecting.

Whereas, if a phone on cluster A is forwarded to PSTN and gets call from cluster B, it just gives fast busy.

I have tried enabling MTP but no luck, any other suggestion?

[TONY SMITH]

Call drop at the point of connection could be a codec mismatch.   I assume you've checked configurations along the path, but something could still be missed there.

I would start by grabbing trace files from the destination cluster, and look at the SIP messages first since they're easiest (for me) to understand.  You should see what termination reason is being sent back to the originating cluster, which is a start.  What is the PSTN connection, is that ISDN/H.323 or SIP?   It's worth grabbing the appropriate and easiest to read debugs from the gateway as well.