SIP Trunking Issue

[jmcornilla]

I am setting up an integration between CUCM8.5 and another SIP PBX that I will be using as my media gateway.  I am able to set up calls from the CUCM towards the SIP PBX but I can't set up calls the other way around.  After some research, I've realized that my SIP PBX sends SIP packets with different contents on the REQUEST-URI field and the TO field.  Is it possible to setup CUCM to route according to the TO field instead of the REQUEST-URI field? As an alternative, can I use scripting to change the contents of the REQUEST-URI into whatever is the content of the TO field?

[Jonathan Schulenberg]

RFC3261 seems pretty clear in sections 8.1.1.1 and 8.2.2.1 that the UAS (CUCM in this case) should be making the determination on whether to accept the call or not based on the REQUEST-URI field.

Is it possible to setup CUCM to route according to the TO field instead of the REQUEST-URI field?

Based on the documentation I can find the answer appears to be No.

As an alternative, can I use scripting to change the contents of the REQUEST-URI into whatever is the content of the TO field?

Yes! The Cisco Unified Communications Manager Administration Guide has a chapter on this titled SIP Normalization Script Configuration. The only thing it doesn't show you is a sample script in the supported Lula language. The Lua webpage has online documentation that explains the language in an abstract fashion but not specifically to CUCM. The only Cisco document I have found on the actual language is Developer Guide for SIP Transparancy and Normalization.