VoIP Failover Design Questions

Unanswered Question
Mar 24th, 2010


We have call manager cluster: One publisher, One subscriber. Also one UCCX server, one voice mail server and ISI server. They all locate at the same place. Right now we are considering a disaster recovery plan for phone system. We have multiple remote sites which have IP phones registered with the main site. Also several contact centers use the UCCX server too.

I was thinking utilize the CME in SRST mode in every gateway at the remote site. But by that way, I need configure every gateway. It seems not good idea. Right now I'm planning to buy another callmanager and UCCX server, Voicemail server at our DR site to do the failover over the WAN. My question is
1. Can I use one callmanager for both publisher and subscriber purpose? I see the normal callmanager cluster is one publisher plus several subscribers. But if the main site publisher
went down, I need another publisher at the DR site. So I need 2 publisher and 2 subscribers in my cluster. If I can use one callmanager for both function at the DR site, then I could save a lot. Any performance degradation?
2. For UCCX server, I'm not sure how UCCX server failover through the WAN. How to design it? Any suggestion?
3. I'm not sure Voicemail and ISI server can do the failover or not. Any idea?

Appreciated for any help.


I have this problem too.
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Aaron Harrison Wed, 03/24/2010 - 07:45


1) You can have only one publisher in a cluster. If the outage of the publisher is for a short time, it's not a problem unless you need to perform admin tasks such as configuring phones etc. If you are on 6+, you can still log in and out of EM with some extra configuration...

If you are talking long-term loss of a publisher, the only option is to restore from backup (to the same IP/hostname server)

2) UCCX will support clustering over the WAN from v8. You need lots of bandwidth (it may use up to 4 mb or so) and max 80ms rtt.. Before that it isn't supported, as it can be unstable if the two servers don't have good connectivity, and if the two servers lose connection to each other they can get into a bad master/master state.

3) What's ISI? What voicemail product do you have?



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hxmengmetro Wed, 03/24/2010 - 08:20

Thanks Aaron,

I think you mean if don't need configure the phone, add the new phone, I will not need publisher in the DR site, right?

We have UCCX version 5.0(2)SR02_Build045. Based on this version, it seems no failover option for us. It's a windows box. I guess I can't rehost it. So the only option is to restore the system and use same IP, right?

ISI is for the accounting and billing for VoIP system. I think it doesn't have to be failovered at the downtime. I will get back to you about voicemail server version. It's a cisco mcs 7800 box.

Thanks a lot.


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Aaron Harrison Wed, 03/24/2010 - 09:00


Yes, unless you need to admin CCM, you can survive without the publisher.

If you use EM, you will want to ensure that you have the EM service enabled on a subscriber and that you have a method of allowing phones to use the other server (typically you have a URL pointed at the publisher IP). Options are:

- A load balancer of some sort

- A second EM URL on each phone

UCCX5 doesn’t support HA over the WAN as described previously... but you could restore it to another site as long as you are restoring to the same IP/hostname.



hxmengmetro Wed, 03/24/2010 - 09:14

Thanks Aaron. We do have EM configured for contact center agents. The consulting company configured that for us. I'm guessing that should be configured through Customer Response Solutions Administration? Where to set that load balancing option? Thanks.


Jaime Valencia Wed, 03/24/2010 - 07:48

No, a cluster is only 1 PUB + SUBs + TFTPs + MOHs. If you have 2 PUBs, then those are 2 different clusters.

You would need to perform a backup on the production server and then a restore.

You need to provide versions, because if this is linux you also need to rehost the licenses.

As for VM, wihout knowing what you have and version no one can tell you if you can have failover. You need to provide enough information.



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hxmengmetro Wed, 03/24/2010 - 08:08

Thanks Java. Our publisher and subscriber version is I guess it should be a linux box? Not sure about VM version at this time. Will get back to you later. So you mean if subscriber is linux box. Then I don't have to buy another subscriber box, right? Also if I don't need add new phone into the backup system when the main site is down, I don't need another publisher, right?


Jaime Valencia Wed, 03/24/2010 - 08:29

Yes that's Linux, the idea of 2 PUBs would mean a backup, a restore and license rehosting.

Not sure what you mean about the SUBs.

The basic principle is your phones will be in the SUBs and only in some circumstances where you only have 2 servers then have PUB as failover. Or leave it as the 3rd option.

And yes, no PUB running means you cannot change anything in the config before recovering it.



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hxmengmetro Wed, 03/24/2010 - 08:57

Thanks Java. So it seems I can rehost the publisher.

Our subscriber has the same version, also a linux box. My questiona about SUB is: We have 1 publisher and 1 subscriber now. Can I install another subscriber in VMWare with the same license from the first subscriber and run it with the first subscriber together at the same time?

If yes, then I can run one publisher and two subscriber at the same time. When the publisher and the main subscriber down at the main site, I can restore the publisher in VMWare with same configuration/same IP at DR site and the 2nd subscriber at DR site can take over the main subscriber's role.

I maybe wrong still. Please correct me. Thanks.


hxmengmetro Wed, 03/24/2010 - 10:28


You mean we still need buy 2 MCS server. One for pub, one for sub. Right?


hxmengmetro Wed, 03/24/2010 - 09:34

I just checked our license. It only allows 2 nodes in the cluster. That means I can't run 1 publisher plus 2 subscribers at the same time. The reason I want to do that is we can failover to the subscriber at the DR site faster. I'm thinking without buying another license for the 3rd node, we could only do the same thing to restore subscriber with same IP/same configuration just like publisher.

Another question: Based on our version Which linux distribution we need to install CUCM? Redhat Enterprise 4? Thanks.



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