Upgraded a customer to 6.1.2 this weekend and ran into a few issues, but got them resolved. I thought I would share them with everyone. I also upgraded the router from 12.4.9T1 to 12.4.15T5.
Inbound calls worked well, but outbound calls had issues. All of the newer phones like the 7961 & 7941 phones did not have the availability to dial out. The call was getting was getting to the gateway, but it kept reporting an error regarding no channels available. Turned around and tested a 7960 phone and all was good. It successfuly dialed out with no issue. Made multiple calls between the two model phones and the results were the same. The 7961 could not call out, but the older 7960 & 7940 phones had no issues.
Decided to downgrade the router back to the orginal version of 12.4.9T1. After doing so, the 7961 phones would successfully dial out, but the returning alerting ID reported back as "Fake_ID".
I figured that 6.1.2 was sending something different in the setup message and was causing this to occure and that the IOS 12.4.15T5 did not agree with it. Decided to upgrade the router to 12.4.15XZ and all is well with the world now.
I'm going to do some research today to figure out what was being included in the setup message that caused the PRI to report no channels are available when calling out on the 7961 & 41's.
If I find something, I will be sure to share it.