CUCM 12.5 Fast Busy Signal 8851 to 7961 SCCP

[Skyhawk92]

Lab environment with CUCM 12.5 fresh install with defaults with 3 phones registered, 8851, 7961 SCCP and IP Communicator SIP.

No partition's or CSS's configured. All devices are in the null partition. CUCM is in the datacenter and phones are at the branch. The phones connect to the CUCM via site-site dedicated IPSEC VPN  tunnel. The phones are on the same local subnet at the branch office.

I can dial from the 8851 to the 7961 no problem, but when I try to dial from the 7961 to the 8851 I get a fast busy tone.

When I dial from the 8851 to the SIP Soft phone i get a fast busy tone as well. 

Real time Monitoring says SIP/2.0 503 Service Unavailable. I don't see any other error messages in the Detailed SIP Message.

Any idea whats going?

Thanks,

[gearbox]

Are all the phones in the same location and region?  Can you post some RTMT logs of the calls so we can see whats happening?

[Skyhawk92]

The configuration is plan vanilla, same region and location for all phones. I am trying to pull some logs from RTMT from extension 4001 (7961) to 4000 (8851) but I am getting an message saying "no message match your search query" and the time is accurate for the run time and timezone. I am able to see logs for a successful call from the 4000 (8851) to the 4001 (7961) but doesn't make sense why I cant get logs from the 7961 to the 8851.

The Termination Cause Code is 1459617833 CCM_SIP_503_SERVICE_UNAVAILABLE

[gearbox]

Can you reproduce your issues and then when you pull the logs just do relative range and select last 15 min.