Adding Remote Site Call Manager Express's into your new CUCM Cluster

Unanswered Question
Oct 27th, 2009

We will soon be building a new CUCM Cluster at our headquarters and will have to support remote sites that have purchased Call Manager Express already. My question is what will be needed to bring the remote sites into the new cluster. I assume we will need to add a route in our routers here but what other steps will be involved to ensure that the traffic from the remote sites will be able to be processed by the new cluster.


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Brandon Buffin Tue, 10/27/2009 - 07:23

The answer depends on your environment. One option would be to use a centralized approach where all phones register with the HQ CUCM and the current CME routers become MGCP or H.323 gateways with SRST (or CME as SRST). In this scenario, call processing is handled by CUCM unless there is a CUCM or WAN failure in which case the local gateway takes over basic call processing.

Another option is to leave the CMEs in place and create a trunk from the CUCM to each branch router to allow extension dialing, toll bypass, etc.

There are certainly advantages and disadvantages to each option.

Hope this helps.


Breemac24 Tue, 10/27/2009 - 08:06

Thanks for the reply. We are looking to provide a centralized HQ solution and have the CME's have SRST functionality. Would I need to provide a route to the HQ routers for connectivty and just register the phones on the HQ Cluster.

Brandon Buffin Tue, 10/27/2009 - 08:10

In CUCM, you need to setup:


Route Groups

Route Lists

Route Patterns

You will also need partitions/calling search spaces to separate calls assuming you want phones at each branch to use their local gateway for PSTN calls. So, you would need a CSS on branch phones that has access to a partition that is assigned to a route pattern that has access to the gateway for that branch.

Hope this helps.


Breemac24 Tue, 10/27/2009 - 11:59

One last question. Is there any other configuration changes that would need to be made on the CME's at the remote sites to make these sites point back to our HQ Cluster.


Brandon Buffin Tue, 10/27/2009 - 12:11

Yes, there is. You will need to configure the routers as either MGCP or H.323 gateways and configure SRST or CME as SRST. See the following links.

Configuring the IOS MGCP Gateway

Cisco IOS H.323 Gateway Configuration for Use with Cisco CallManager

Configuring CME as SRST

Hope this helps.



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