I just did a big Asterisk based phone system for an Army base in Louisiana. If the company that brought me in hadn't had tremendous pull and the deadline so short it wouldn't have gotten in at all.
What we built was total overkill for what they're using it for..it was a high availability cluster, 400+ available extensions of which about 50 are currently used and 320 turned on, punched down to T1 channel banks with FXO ports that eventually are terminated miles away, and integrated with a private cell phone network. The PBX system was CentOS 5.2 based and even though Redhat Enterprise Linux 5.2 is an accepted platform (they're virtually the same thing) they about came unglued because it wasn't on the accepted list.
There is no reason that CentOS couldn't be on their accepted OS list except that the 'manufacturer' pays for the very expensive certification process which unless a bunch of interested users chip in will never happen with CentOS. Redhat is the only linux distro on that list as far as I know. I'm already planning on a system based on RHEL instead in the event that they want other phone systems - even if I never get an order for one.
JD
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JD Austin
Twin Geckos Technology Services LLC
jd@twingeckos.com
480.288.8195x201
http://www.twingeckos.com
Stephen Leacock - "I detest life-insurance agents: they always argue that I shall some day die, which is not so."