Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 
Community Member

Multi-Site WAN With Centralized Call Manager

The customer has HQ with 15 Branches. Head quarter has about 4300 Phones, and Branches has:

Branch 1 = 420

Branch 2 = 256

Branch 3 = 385

Brnach 4 = 298

Branch 5 = 262

Branch 6 = 171

Branch 7 = 200

Branch 8 = 97

Branch 9 = 198

Branch 10 = 254

Branch 11 = 269

Branch 12 = 224

Branch 13 = 90

I would still like to propose Centralized Call Manager Cluster with SRST, but little confused since the number of phones per branch is very high.

What would be best deployment model for this type of scenerio along with VoiceMail and CER.


Re: Multi-Site WAN With Centralized Call Manager


You could still run centralized model with SRST at the branches. 3845s can handle up to 720 phones in SRST mode. If you use SRST, you need to make sure you got enough bandwidth on the wan to support signalling traffic and rtp (inter office calls) for that many phones.

Since the no. of phones are that high, it should be a very critical branch office. The cost of a 3845 bundle is 12-15k. I may suggest you spend that kind of money on a server for that branch and use the following options.

a. use a separate cluster over those branches

b. or use clustering over wan. Make sure you got the 40ms RTT required for SQL replication to work properly.



PS: please remember to rate posts!

Hall of Fame Super Silver

Re: Multi-Site WAN With Centralized Call Manager

I agree with Sankar and would propose deploying CCM Subscribers at the large branch sites, you can have up to 8 call processing CallManagers in a cluster. Mkae sure that bandwidth is not an issue as the SQL replication between CCMs will need about 900 kbps.


Community Member

Re: Multi-Site WAN With Centralized Call Manager

Are you guys suggesting to deploy Subscriber at each office if the bandwidth is not an issue. This won't be possible due to have branches more than 8, and currently there are 15 branches or deploy subscriber in fewer branches with phones around 420, 385, 298 respectively.

If bandwidth is an issue than I can go for multiple culster such as clusters in HQ, Branch 1 (420) phones, Branch 2 (385) phones, and Branch (3) with 385 phones, and Branch (4) with 298 phones. Other locations can be part of the HQ Cluster.

With Multiple Clusters, Would CME/CUE a good choice for Branch Locations?

Any Help will be appreciated.


Re: Multi-Site WAN With Centralized Call Manager

Of course you can use CME/CUE, but the problem is that you need 3845 for SRST with CME/CUE, which cost a lot of money CISCO3845-CCME/K9 is $16495 plus CUE ($3000, not include voice mail subscriber box).

So I will agree what people suggest here.

I have centralized design (Publisher, subscriber) at Main Location, and another subscriber at remote site coz 500 users. I chose put subscriber there rather than use 3845 with SRST.

They share voice box at Main site (Unified).

The rest of remote site use SRST for backup.

Large remote site with T1 PRI with SRST if WAN down.

Small remote site with vic2-2fxo/4fxo with SRST if WAN down.

You can read the SRND here:

Also, you can design multiple cluster depends the location of main and branches. For example, half office located at West Coast, another half at East Coast. If I were you, I will create two clusters.

Again, it depends a lot of things, for example bandwidth, round-trip delay etc...

Hopefully, thats can help you.


Hall of Fame Super Silver

Re: Multi-Site WAN With Centralized Call Manager

Deploy CCM subscribers only at some of the larger branch sites, the rest should be fine with SRST.

CME/CUE is a good solution, but I would not suggesr it for your deployment as you would loose the enterprise feel, i.e. forwarding voicemail messeges, VM distribution lists, CCM features like Extesnion Mobilty, uniform dialplan, etc.


Re: Multi-Site WAN With Centralized Call Manager

I have a similar design I am looking at. What if my remote site with 300 IP phones had IPCC enterprise and 100 agents? Still just one subscriber at the remote site, IPCC at remote site and failover at HQ?


Community Member

Re: Multi-Site WAN With Centralized Call Manager

No one has addressed the CER design.

Should there be CER at each site to create one large cluster or can you centralize this at the publisher site?

Also, can you track phone movement on switches across the WAN from the CEr servers or will those phones need to be manually changed in teh CER datebase?

Hall of Fame Super Silver

Re: Multi-Site WAN With Centralized Call Manager

You can use one CER cluster (up to 2 servers) which will support up to 30,000 phones and 2,000 switches. And yes CER will track phone movement accross WAN just fine.



Re: Multi-Site WAN With Centralized Call Manager

I agree, i would only use a centralized CER for phone movement. The 911 aspect of the unit is still a little sketchy to setup. It's quite ocmplicated and the local LEC's are not very good at understanding all this with the CER

Community Member

Re: Multi-Site WAN With Centralized Call Manager

I agree that the product is "sketchy" to say the least. We have set up 4 LAN only implementations where all the phones are local to the servers. How does it work ofver the WAN. Does all the phone activity get passed via SNMP? If so what is the use of CDP on the servers?


Re: Multi-Site WAN With Centralized Call Manager

I think CER does work best when you know all the caviats to the product. My biggest problem is getting all the switch ports to the locations mapped out correctly and then getting it updated in CER. Once it is set, phones can move whenever they want. (hence no one changes the cables in IDF room either) It's all pretty much done with CDP The phone registers with CallManager, CER is assigned to CCM. The CER pulls info from the CER and then tracks them down with the switches loaded in the ERL.

Community Member

Re: Multi-Site WAN With Centralized Call Manager

Some other engnineers suggested to either go with Centralized Call Manager Cluster with SRST. He suggested that Clustering over IP/WAN can be problemotic if RTT is not met or if the distance is more than 3000km.

Other option he suggested to go with multiple clusters. For example,

HQ and closet branches can be in one cluster.

Combine 3 or 4 branches, and put them in a different cluster where branch with the most users should have CCM servers, and smaller branches in that cluster will run SRST, and so on. In other words, combine the branches that are close in their own cluster.

The only issue now is if each cluster will need a separte pair of CER or one CER pair can support multiple clusters.

For Unity Voice Mail, will have to configure Digital Networking.

HQ is a campus enviroment, and customer wants to go with the best possible design when it comes to calling 911 for the HQ and for all the brances.

The question is with keeping 911 mind what be the best option:

Centralized Call Manager with SRST.

Cluster over IP/WAN for major branches and SRST for smaller branches, and or

Multiple Clusters.

Any help will be appreciated !


Re: Multi-Site WAN With Centralized Call Manager

I'm going to push the still for a centralized deployment of CCM. But, putting a Sub at my remote site and creating a PTP link between the two just for the heart beat and data replication for the Pub-Sub. My remote sites with smaller deployments will still have SRST back to HQ, but be able to failover to either site. For whatever reason, my MPLS network has too much latency on it and that's a whole nother issue. For Pub to Sub accross a wan, Cisco says 40ms rountrip. Industry average is 8ms per 1000 miles for any network... so I should be within the range for where i am going to (1260 miles). I have seen other networks setup this way, but with latency in the 40-60ms and ccm has been fine... all depends if you can cisco to buy off on it. I would not under no circumstance split an IPCC prim and secondary.. I have heard horror stories of "headless" servers....

CreatePlease to create content