[cisco-voip] Extensiom Mobility redundancy in cluster over WAN

[Wes Sisk]

the key here is to make the extension mobility URL redundant. there are 
a couple options for that:
1. redundant dns - em service url uses hostname. phones do dns lookup 
against local dns server.  dns server returns IP of reachable cm server
2. SLB feature in content switches and c6k - establish a virtual IP on 
your switch. the virtual IP redirects to whatever backend server is 
currently online/available.

I believe this is discussed in the CM6.x SRND at 
http://www.cisco.com/go/srnd with the advent of "user facing features" 
redundancy.

Regards,
Wes

On 11/11/2008 3:39 AM, keli at carocomp.ro wrote:
> I'm trying to figure out the best way (or rather a working way) for EM 
> redundancy in a cluster over WAN setup. It's a 6.1(2) cluster, so EM 
> should work even when the first node is down.
>
> I've read the SRND, but the solution therein doesn't works for me 
> completely:
>
> - I can have a virtual IP through SLB for server failure resiliency
> - I can add multiple service URLs for extension mobility login/logout. 
> Though this could be somewhat confusing for users, if it adds to the 
> reliability, the better.
>
> However, a SLB IP still has to reside on a router on either side of 
> the WAN. What to do in the case of a WAN failure? How Can I ensure 
> that EM will still work on both sides of the WAN (there are only two 
> major sites, btw) in case of a complete WAN outage?
>
> Since EM is extensively used here this would be rather important to be 
> reliable.
>
> thanks,
>   Zoltan
>
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