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Multi-Site CME with Distributed Call Processing

Hello  All,

I'm trying to setup a CME system that will span 2 very small offices that will be connected via site-to-site VPN.  Each location will have PSTN connectivity via FXO.  3725 router with Catalyst 3524-PWR on each site.  7970G phones.  The goal is to have calls come in from the PSTN at either location and be answered by an employee at either location, i.e;

Location A: Call comes in from PSTN to 555-555-1111 which is a DID assigned by PSTN to location A, it rings DNs 1001 and 1002 (which are local to Loc-A) and also rings DNs 1005 and 1006 (local to Loc-B)

Also if a call comes in from PSTN to 555-555-2222 which is a DID assigned by PSTN to location B, it rings DNs 1005 and 1006 and then will ring 1001 and 1002. 

Basically, I know this is confusing the way I have tried to explain it, but am looking to integrate 2 offices with different DIDs assigned by PSTN to each office using CME.  Enable call transfer between each office, etc.  If anyone has any suggestions I'd welcome them.  Also if there are any Cisco documents that work with this type of scenario using VPN to link locations I'd also be interested in reading them.  From what I understand, CME would be a good match for this situation.  Thanks in advance.

New Member

Re: Multi-Site CME with Distributed Call Processing

I have never tried this scenario but I would start with hunt groups. "voice hunt-group x parallel", the parallel keyword triggers a broadcast hunt group, you define a pilot number as usual and a list as usual but the numbers in the list will all ring at the same time. The only question would be the behaviour of some of the numbers being across a WAN/VPN link. Its worth a shot though. And of course the "conn plar" on the FXO port would point to the pilot number on the hunt group. For additional references, Cisco refers to this as " parallel hunt groups" or " call blast".

Re: Multi-Site CME with Distributed Call Processing

Hi, I have read your idea twice and I can have some comments on your design concept. I'm discussing some other related technologies besides of your 'shared line' design concepts.

- As your site is over VPN clusters, bandwidth is an issue for sure, never forget to design proper qos.

- For your design considerations your number of travelling calls over WAN might be more than the expected, there's much probability to degrade the quality of calls if your don't consider cRTP, proper codec selection and of course the RSVP as well. Consider the ICCS signaling bandwidth to be on safe side. You can get the detail here from this link:

- Consider to send the calls rerouted over PSTN if you can't send them over WAN for the lack of proper BW.

- After all those plans configure simple 'shared-line' concepts to implement your CME features like ringing all inter-cluster phones at a time.

VPN should not be an issue if you take care of necessary ports passing though your firewall. You can get the port details from this link:

Though the link is for CUCM but it would be applicable for CME as well.


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