Config needed for multisite IP telephony over WAN

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Apr 5th, 2007
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I would like to implement a simple multisite IP telephony over the WAN/internet, with single call management at the main office. We run a CCM cluster, version 4.1.3

What I would like to implement is exactly what is shown on figure 2.2 on the following link:

Our network at the main office runs with 10.X.X.X unroutable addresses, and the branch office has one public IP address, with a very high bandwidth link (100Mbps).

I would like some config examples for the routers needed at the main office and at the branch office to support the IP Telephony. If there is a complete example, including CCM config to support the branch office, that would be even more appreciated.

Thanks, Frank

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paolo bevilacqua Thu, 04/05/2007 - 07:49
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Do you want the voice go over crypted VPN, or are you ok with no cyphering ?

paolo bevilacqua Thu, 04/05/2007 - 08:46
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Good, beside newer CM software supports secure voice natively.

For the branches, you don't need to do much. Regular NAT config on the router be enough because Cisco IOS supports SCCP in NAT. Just configure the DHCP server to give TFTP address as CM's. In the HQ, you will need static NAT make CM reachable form outside unless you want to expose one of the interfaces to the Internet and apply some windows filtering for security.

I'm not very good at CM but I suppose it's just about adding one or more "remote endpoint" and that's it.

sitel_uqam Thu, 04/05/2007 - 11:10
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Thanks, for the pointers! By any chance, would you have a URL to a doc containing a "typical" config that would give me more details on how to do this? That would save me a lot of research time!

Thanks again,


fdefilippo Thu, 04/05/2007 - 12:44
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For All sites you can consider to set up GRE Tunnels one each other.

One or all branch office can be equipped with Voice card useful for example:

- Voice Backup (Route Group List)

- Local calls

- Local SRST in case of wan failure


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