Considering Asterisk Remote Site - Advice?

I work for an automotive dealership. At various times throughout the year, we’ll have an off-site tent sale. I have a vision of a way to improve this by using Asterisk and was wondering if anybody had experience or advice for me.

Background:

We contract a third party company to handle our IPT system at the dealership. We’re running Cisco Call Manager 4 and have a mix of Cisco 7912 and 7960 phones in place.

Basically, a tent sale involves the rest of the people in the dealership moving all the cars a few miles away and my setting up a ‘command center’ of sorts. I have a Slackware box with a couple NICs in. This machine connects to the internet via a 3 megabit wireless link, connects to our dealership’s Cisco VPN concentrator, and provides masquerading services (NAT) to whatever machines I want to wire in. There’s a printer hanging off this machine, which is shared to the local machines via Samba. I have a few laptops as well, which connect via a standard WiFi router that’s cabled into the switch. This way, everybody can use the resources of the dealership, connect to our dealership management system, etc. The VPN software only has to be running on the gateway box, saving much trouble and hassle setting it up on all the machines.

When I tried connecting a Cisco phone to the remote system after the VPN tunnel was established, it wouldn’t boot up no matter what I tried.

My Vision:

Since setting up that Slackware box, I’ve learned FreeBSD and am liking it more and more the longer I use it. We have our e-mail server running FreeBSD. I have a spare machine ready to go, just in case the primary goes down. This machine ordinarily isn’t used for anything and since our tent sales only happen for a few scattered weeks out of a given year, I thought it’d be a perfect opportunity to put this idle machine to use. Our e-mail server has been up for a year without so much as a hiccup, so having a spare box is probably overkill for it anyways, though I want to err on the safe side.

I’d like to throw a fresh hard drive in this system (AMD Athlon 2000 with a gig of RAM), install FreeBSD, set up the VPN/gateway, and get Asterisk running on it. (There’s a port for Asterisk, so installing it should be a snap. There is not a port for the Cisco VPN software that I saw, so I’ll have to check into that.) I would interface Asterisk over the VPN with our Cisco CallManager server. (I read quite a while ago that this is possible by using an H.323 bridge and that you just tell CCM that a range of extensions lives over the bridge, but that’s about all I know at this point.) I could then hang a few IP phones off the switch at the tent sale, whether wired or wireless, and they could call back to the dealership, calls could be transferred back and forth, etc.

Questions:

Will Asterisk interface/integrate with Cisco Call Manager 4.2? If yes, how would I set this up on both the CCM and Asterisk? Will it work over a VPN?

What phones would be appropriate to purchase for use with Asterisk? I assume that there’s a ‘supported phone’ list somewhere with known issues with each model, but I’ve looked and cannot seem to find it. I need to keep this project as low-cost as possible until I prove to management that it works and is useful, though I don’t want to get junk either. Looking on flea-bay has indicated that I should be able to get a decent SIP phone for $40-50, but without a ‘supported phone’ resource to consult, I have to google each model and try to find if there are issues with getting it to work with Asterisk - a very time-consuming and inexact process at best. Since this is the first time I’m going to be touching Asterisk or building an IPT system, I want to make things as easy as possible for myself.

Would purchasing ATAs and hanging a regular analog phone off each be a better solution? I’m guessing that this is how I’ll want to do any cordless phones, if for nothing other than cost. (A good analog cordless phone = ~$25, cheapest cordless IP phone = $120+) It also would eliminate any potential firewall issues due to the WiFi router being between the phone and Asterisk server.

Is there anything else I should be aware of or consider before starting to buy and put stuff together? I know this is a very open-ended question, but like I said, I’ve never done this before.

I’ve done stuff like changed extensions and the like on our CCM, but the rest of the terms are like a cloud in my brain; don’t have a real firm grasp on them and don’t know how they relate to each other quite yet, though I’m looking forward to learning. I’m able to pick up tech stuff very quickly. I’m still very much in the preliminary stages of designing this system and don’t want to build something that would be better designed a different way and that’ll be difficult to change down the road.

Thanks in advance for any help, advice, pointers, or links.

Bump - Anyone?

Phones that are supported by asterisk are any SIP phone, or IAX2 phone.
You can buy cheap ATA’s and connect an analog phone to them, You can integrate the Asterisk system by using an analog extension from the Cisco CM or If it can provide a SIP trunk, or a SIP extension(I dont know to much about the CM). I would think as long as you had a connection to your network it would work. If you want to keep the cost down, you can use Softphones first, then purchase some hard phones or an ATA, in order to keep cost down at first.