How to migrate to a VOIP

Unanswered Question
Oct 25th, 2007

I'm the network engineer at a small company that would like to migrate to VOIP to save money over long distance calls to other remote site.

How do I go about it?

I have this problem too.
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Paolo Bevilacqua Thu, 10/25/2007 - 09:30

First decide if to replace your PBX with voip based or not.

If so, you can look at cisco callmanager express that is simple to install and administer. This works natively over internet, VPN, or any IP base network.

If you keep your PBX, you just install an appropriate router connected to PSTN, PBX, and the Internet or other transport service.

You will program it so that long-distance calls are sent over a no-cost media.

That is basically it.

Hope it helps, please rate post if it does!

mooreg7464 Thu, 10/25/2007 - 11:54


We had talked about it and have decied to go with a total Cisco VOIP solution. I'm thinking the setup would be something like the following right, Cisco phones 7940s to Call Manager(phone call&feature setup)..Unity for (voice mail), and for offnet calls to router thru media gateway to handoff to local PSTN(Bellsouth).

My next question would be is which equipment would I need to order to support 35 users.

How would layer1 look like, and which protocols to setup between phones and call manager(sip or just tcpip).for call manager to gateway(sip too)and gateway to pstn(ss7 over ip or sip)..

Will 911 call functions work also?

If you could provide me with a base line of layer1 drawing, and necessary equipment needed for this solution would be most greatful.

Thanks in advance,


Paolo Bevilacqua Thu, 10/25/2007 - 12:30

Hi, for 35 users you can use either a 2811 or the integrated uc520 in the 48 users version.

That would be CCME that works much like CallManager but without the need for a dedicated server, all is done in the router.

You can still add callamanger at a later time if you want, but CME as I said already do all what an offoice wants.

The best way to connect to PST would be with ISDN PRI or BRI.

The 7940 is not manufactured anymore, the equivalent is the 7941 and also a nice one is the 7931. You also need a PoE switch like a express 500 series to power the phones, eliminating the power brick that is a nuisance.

Of course calling 911 will work.

Do not worry too much now about the configuration, as if you are not of the trade it would be better you have reputable cisco partner do it for you initially.

Hope this helps, please rate post if it does!

mooreg7464 Fri, 10/26/2007 - 06:21


Thanks for your earlier response. So if I understand you correctly I should have the following.

Central Site: 35 to 40 users

5 meg to Internet & PRI to PSTN-->Cisco 2811 to Cisco 3750G-48PS to -->Cisco 7965G IP Phones-->PCs

All remote sites will have IPsec over GRE to allow EIGRP network to route..Each site share files between them

3 Remote Site: 4 to 6 users

1.5 meg to Internet & BRI to PSTN-->Cisco 1861 to Cisco Express 500 switch to-->Cisco 7945G phones to-->PCs

I believe I have the setup right now, thanks to your help. I do want to make sure that each remote location can call other sites and central site without going "offnet".

Do I have the setup right? Is there anything I should change?

Thanks in advance!


Paolo Bevilacqua Fri, 10/26/2007 - 07:15

It is right.

Only, the 7965 is not yet officially support on CME, altough I think it will work configured as 7961. You also need upgrade the PVDM2-16 that comes with the 2811 bundle, with another -8 or -16 to get more channels.

You need VWIC-1MFT-T1 ow VWIC2-1MFT-T1/E1 to connect your PSTN PRI. Also get a vic-xFSX to connect your faxes, wireless phones, etc.

If you want voice mail at the main office (that you can use networked to branches), also get AIM-CUE or NM-CUE. The latter supports more users.

Note, the 1861 has just been introduced, it may take a while to deliver. However it has an 8-port PoE switch so you can possibly do without the express 500.

They all will be able call each other, you can configure a "static" dialplan or use like SIP registrar or h.323 GK, but these are configuration details.

Hope this helps, please rate post if it does!


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