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I want to implement one scenario, Supose  2 locations A and B both are in same city say in Delhi, and we have 2 MSC servers for IP phone and customer want 1 MCS server should be installed at A  (publisher) side and other should be installed at B (Subscriber) location and we have only one router at A location for PSTN, Now if one of the MCS Server at Location A failed , and we have  router at A location, so we have server at B location and router at A location so are authorize for the this kind of scenario to make a PSTN calling.




Re: Scenario

It's not ideal but you can do that.  You need to make sure you meet the bandwidth and latency requirements for clustering over the WAN which is in the CUCM SRND for the version you are installing.  Additionally, you would want to consider the impact to bandwidth on the WAN link from Site B to Site A for calls traversing that link to hit the PSTN gateway because inbound PSTN calls destined to Site B phones as well as intracluster calls (calls from IP phones at Site A to Site B and vice versa) will also be travelling that link.

My recommendation would be to have at least one gateway at each site.  If possible, let each site use it's own gateway for at least outbound traffic.  In addition, if there is a loss of the WAN link between sites - then phones at each site could register to the local CCM and have a local gateway for outbound calls.  Inbound calls for each site would depend on your number range and how the telco routes incoming calls (i.e., all thru one trunk - Site A - or split between PSTN trunks based on number).


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