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New Member

CCM cluster across the WAN - What would you do?

I have a CCM 3.2 cluster distributed across the WAN. I have 1 publisher and soon 1 subscriber in a central location. At large sights across the WAN I have installed their own subscribers. Smaller sights are using the central server for registration and 3725's and 4224's is SRST. Bandwidth between sites is not really an issue. We're talking at least 3 mbs and usually much more.

How would you have deployed? I'm wondering how many of you would have made the larger sites their own individual CCM clusters? How do you make calls between the two sites? I'm just reviewing for my own peace of mind if I'm going about this the best way and figured I'd bounce it off you all.

New Member

Re: CCM cluster across the WAN - What would you do?

I would suspect you are going to run into problems with the remote subscribers. Cisco, last I heard, doesn't support cluster spread over any WAN, regardless of bandwidth. It's not the amount of data, it's the speed. The SQL replication breaks down if there is *any* delay. I would suggest either centralizing your CallManagers and relying on SRST in case of WAN failure or put Publishers at the remote sites and Inter Cluster trunk them. In the former, you'll have greater initial expense for the SRST licensing. In the latter, more headache administrating it. But in either case it will probably work better than distributed over a WAN.

New Member

Re: CCM cluster across the WAN - What would you do?

So far we haven't had any problems with replication with this setup and our Cisco SE hasn't indicated any problems with our proposed plans for new sites.

New Member

Re: CCM cluster across the WAN - What would you do?


1)It all depends on how may users you have at these sites and geographic placement.

Making calls between the sites using regions loacations intercluster trunks to other clusters or Gatekeeper though in your case probably not

CAC through locations or GK

LLQ on wan for signalling priority...

If you can justify another cluster good.

Otherwise centralised with SRST for wan failover is the Cisco advertised prefered method.

Their is no documentation that says your topology is supported.

Personally I would stick with centralised CM's

Its just more practical.

What if you upgrade the cluster do you Hire a chopper to remote sites to upgrade the Subs or rely on vnc and OSS support staff.

More subs more cash +unsupported not the best idea.

Tell me why have you designed it it the way you have.

Perhaps there is method to the madness.


New Member

Re: CCM cluster across the WAN - What would you do?

Well, at the proposed new site there will eventually be 400 phones. Instead of using SRST we decided to throw a subscriber there for survivability.

I'm not worried about upgrade issues. Thats not a bid deal.

We have 7-8 campuses in our university system. We've been asked by the state to cut costs. One way of doing that is by cutting long distance expenses between campuses. Each campus has their own phone system. Some are Nortel, some are Avaya. But at the same time we are tieing these phone systems together we are also looking for opportunities to serve parts of the campuses that don't use the local phone switches. I didn't really want to get into supporting several hundreds of phones with SRST. By putting a subscriber at each of the sites and having all registration done at that subscriber we eliminate the need to register over the WAN. If the WAN goes down for whatever reason, that site doesn't notice because they still can contact their local subscriber, thus eliminating the need for SRST. Also at all the sites there will be voice gateways providing access to that sites local exchanges. The whole university system can than call those exchanges, no matter where the call is being placed, toll-free.

One of our SE's, who works for the voice group never said don't do that. He knows our plans and helps out with implementation.

Like I said, we've never had a problem, but I'm getting a little concerned that I may be going about it the wrong way.

I do appreciate the responses. Thanks.

New Member

Re: CCM cluster across the WAN - What would you do?


I thought I would add some more insight to this thread. What you are proposing does work but there are some caveats.

Besides the Bandwidth available between the two CallManagers required for Database Transacations (900 Kbps for every 10,000 BHCA), you must adhere to the Round Trip Latency limitations as well.

Between any two CallManagers you cannot have more than 40ms Round Trip Delay.

If your WAN is high capacity(BW) and Low Latency with QoS, you should be OK. The various deployment models are very well documented (Page 1-14) in the following Cisco document "Cisco IP Telephony Solution Reference Network Design Guide, Release 3.3, May 2003". Keep this as your "Bible" for Cisco IP Telephony Design. This link provides access to many of the Cisco great solution design guides:


Good Luck.


New Member

Re: CCM cluster across the WAN - What would you do?

Well their you go.

Clustering over the wan.

Just the model you want.


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