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CallManager Failover


1 CCM 4.1(3)sr1 cluster with 4 Subscribers & 1 Pub.


The servers in our cluster were configured with antivirus software that had a memory leak which caused one of our Subscribers to run out of available memory. The bigger problem was when the server became low on resources it lost SDL link to the cluster, but was able to maintain IP connectivity to its registered phones. This created a situation where 1/4 of the phones on the cluster were basically inoperable and did not fail over to their secondary CCM server.


1) Has anyone seen a similar situation

2) What determines whether a phone fails over? Is it purely based on IP connectivity to the primary CCM?

3) Would it be possible to configure CCM to somehow failover the phones registered to it if SDL link is lost to the cluster?

Any input is greatly appreciated.



Re: CallManager Failover

Phones failover b/c they cannot communicate with the current callmanager. It is purely TCP/IP based. No, it is not possible to have it fail b/c an SDL link is lost and you probably would not want it to. An SDL link would be lost if any CCM went down. SDL links exists between every server (full mesh). If one went down, then all phones would unregister. CallManager can be deployed across a WAN. If the WAN went down, the SDL links would go down, and then the phones would unregister. There are plenty of reasons why you wouldn't want to configure failover based on SDL links going down.

What you could do is set your keep alive timer to the phones to a shorter period. If you ever had another memory problem, and it was taking too long to process keep alive timers, then the phones could failover more easily. The problem with that is putting unnesessary load on the callmanager during normal operation.

New Member

Re: CallManager Failover

Great Information, Steve! Thanks for taking the time to explain the process. It is very helpful.