<div>All,</div>
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<div>I am in the planning phase of a multi site system for voice. The two choices I was looking at are 1. Asterisk and 2. Cisco. I am comfortable with Asterisk and like a lot of the features but there are some things that I like better about the Cisco solution. Each office (only three planned with some home users as well) will have no more than 20 users. The goal is to cut costs on dedicated lines. Here is the plan, please let me know if this is feasible.
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<div>2801router at each office interconnected to the main office via VPN.</div>
<div>SIP trunk from remote offices back to main office</div>
<div>2 PRI lines at the main office</div>
<div>2 POTs lines at each remote office for backup and 911 access.</div>
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<div>We would like for all calls to route over the SIP trunk from the remote office to the main office and out to the PSTN there and from a number on the PRI in the main office routed to the remote offices. In the event of an Internet outage anywhere in the mix, we would like the failover to go out of the POTS lines and we can call forward to the POTS for inbound. We are aware that our concurrent calls at the remote office at this time would be limited to 2 but at least things could still function. We also had the idea of adding a SIP provider for each location in case the lost connection is with the main office only. This way they could route via POTS or to the SIP provider.
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<div>My questions are the following:</div>
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<div>Is this feasible with Cisco routers and if so can I use Call Manger Express on the routers to do this or will I need to do a full Call Manger install. </div>
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<div>In either case. Can I use an external system such as Asterisk for Voicemail, Conferences, etc with both CME and Call Manager?</div>
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<div>Thanks for the suggestions.</div>
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<div>Curt</div>