Unanswered Question
Feb 16th, 2010
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          Dear all

I am using cisco callmanager 7.1 cluster and a sip trunk as gateway

more than 12000 ip phones are added to my cluster.

i want to know is there any limitation for this amount of users on my sip trunk?

is cisco callmanager sip trunk limited foe concurrent calls?

thank you

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Tommer Catlin Tue, 02/16/2010 - 08:58
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Where are you trunking to?  If you are using a CUBE, these do have limits based upon the hardware the amount of concurrent calls it can handle.

You may also want to check the capacity planner.

Capacity Calculations

The Cisco Unified Communications Manager Capacity Tool (Unified CMCT)  enables you to calculate the capacity of the Unified CM system for  various configurations. The capacity planning tool is currently  available to all users with a login account. If you would  like to verify the capacity of your system design but you do not have  access to the Cisco Unified CM Capacity Tool, please contact your Cisco  Systems Engineer (SE) or the Cisco Technical Assistance Center (TAC).

The Cisco Unified CM Capacity Tool is available at

ahsan.ismail Tue, 02/16/2010 - 11:34
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I checked the link

but it was not talking about limit on concurrebt calls on a sip trunk

Tommer Catlin Tue, 02/16/2010 - 12:37
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Its going to be limited by a number of factors.  The capacity planner helps you figure that out.

So for example, if your Provider has  SIP trunk to a CUBE, the CUBE has a limit as does the PSTN provider. (bandwidth usually)  on the CUBE it is hardware/software resources.

You also have to determine the number of devices supported in the cluster.  If you have 12k phones, it depends on what type of phones, this then determines the number of servers in the cluster, failover, MGCP, CTI, Media resources, etc. 

So there is more pieces to the puzzle then just max call.  You cant terminate 12k calls onto one CUCM server.


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