Somewhere along the Asterisk learning curve I guessed that this would work and it did. My company has an aging Cisco Call Manager system which communicates with a 2651XM to speak to the telco via H.323. After configuring Asterisk for H.323 we made a few mods to the router configuration and presto, we can make and receive (on our spare DIDs) calls with Asterisk while Call Manager is still operating normally.
As we have difficulty getting reasonably priced support for our vintage Call Manager hardware and software, I feel much better that I have a viable backup PBX for almost no money. It’s been a lot of effort, mind you, having to learn Linux almost from scratch, telephony protocols, Asterisk, etc. etc., but in the end I have much more confidence that I’m not going to be embarrassed by extended downtime.
Asterisk, the phones and the router are all configured to talk u-law so Asterisk goes into packet2packet mode for the connection. We’ve been testing using a 4 year old laptop as our server and it doesn’t seem to put much load on it at all. Even a gsm to u-law connection has no noticeable impact on cpu utilization.