Cisco 7941 Places Calls in a Strange Manner...any ideas?

My Asterisk server has an IP of 10.0.0.225. I’ve got two different types of phones in use, Cisco 7912 and Cisco 7941. The 7912s work flawlessly for everything, MWI, calls, etc. When I place a call with them (extension 5022, for example), the channel is SIP/5022-xxxxxx, and all is peachy.

The Cisco 7941s, however, don’t open the channel like that. They open the channel as SIP/10.0.0.225-xxxxxx, and I can’t for the life of me figure out why. Now, this would normally not be an issue, as I’m using the 7912s for my agents, and I can properly track those calls via the AMI, but I’m also using the iSymphony operator panel, and it also works via the AMI, so unless the channel opens normally, there’s no way it can track the status of the extension.

I haven’t tried it with just a single extension on the phone, because I need two extensions on them regardless (one for paging and intercom (successfully implemented), and one for calls), but I’ve gone over the config files for the phones all over the place, and I just can’t find it.

Has anyone else run into this before and have a suggestion for me? I’m all ears, as this is the absolute last “feature” I have to work out before I can start talking about a roll-out.