I'm trying to implemement a SIP trunk on CCM 4.1.3 and because SIP support is very limited on this version ( G.711 codec only, no digest authentication) I'm forced to look for a workaround since upgrading to CCM 5, which includes an RFC 3261 compliant SIP implementation, is not a feasible option right now.
I successfully could interconnect the CCM and an Asterisk server, so the Asterisk server works like a sort of B2B User Agent, sending the Digest Authentication credentials to the ITSP provider and it seems to work fine letting me use any IP Phone on the CCM cluster to place calls using the SIP ITSP, I cannot place G.729 calls yet but I think it's just a matter of configuring the Asterisk server to perform transcoding and getting the G.729 codec license for the Asterisk server.
Now my question is, is there any option in the Cisco world for doing this kind of setup, I mean maybe an IP-IP GW with SIP support registering SIP accounts with the ITSP on behalf of the CCM 4.1.3 or any other option, is this possible ? I've been struggling with this with no success so far.
Thanks a lot for your advice.