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New Member

Call Manager Architecture

I have two site with one CCM and some IP Phones in each. The WAN connection is a Leased Line with 128Kbps.

It's possible to backup one CCM by the second if it's fail ? and vice versa ?

New Member

Re: Call Manager Architecture

Hi Med,

I am not sure exactly what you want. Do you want two CCMs on either side of the link or you want two co-located CCMs?

Cisco does support this feature and suggests its implementation where possible. One CCM will be the publisher and the other subscriber. You need to configure your gateways as well to reflect this. At any one time, all your devices should be registered on one CCM with the other as a backup.

If your major concern is link unavailability, you may be better served by having a redundant link between your two locations.

The Cisco website has a lot of info about this. Pls. check it out.

New Member

Re: Call Manager Architecture

If I understand correctly you are trying to have a single cluster with a 128k Frame link in between call managers. This is not advisable. Cisco recommend minimum 10MB inbetween Call Managers. I heard rumours that this was going to be reduced in new design guides, but I can almost guarantee that it will not work over 128k. Databases need to be replicated across this link. Also call setups/teardowns voice calls, phone firmware loads, MOH, conferences all need to use this link.

Solutions would be to have two call managers at each site, or to have both call managers at one site and use the SRST functionality of the Cisco Gateways to provide resiliency. However if you use the second centralised call processign model, I would recommend upping the frame speed to 512kbps.



New Member

Re: Call Manager Architecture

Nope 128k is not enough Im afraid, its true that 10mb LAN is recommended but you can use a WAN under the right circumstances with queuing etc (see the design guidelines).

Its not so much that bandwidth thats a problem (although 128k it definately too low) its more about the response times from CM to CM, as when a phone registered to CM A trys to call a phone registered to CM B it needs to know if that phone is on a call, this exchange of information needs to occur in under 40ms I believe. Of course on top of that there is database replications etc etc..