Mulitple CER on single CUCM cluster

[Dave1224]

I can find references to CER limited to one CER group per CUCM cluster but not a reason why. For example the 11.x SRND says "There can be only one Emergency Responder active per Unified CM cluster" but doesn't give a reason. Is it licensing, support, complexity or a technical limitation?

Issue: Customer has multiple sites with single CUCM cluster and wants a local CER at each site in event of WAN failure. Each site has a local CUCM subscriber. 

[Chris Deren]

It's just the way the application was developed, tested and supported, no specific reason was provided AFAIK.

Does the customer have local CUCM at every one of these locations we well?  Because if not then having local CER would not buy them much anyway.

In either case the way I always handle CER failure (in your case assume local CUCM remains active) is to use standard local route groups as backup to the normal 911 dialing, so if both primary and secondary 911 CTI RPs are down call forward unregistered on 911 CTI RP forwards the call to pattern that points to SLRG which can point to local GW (assuming this is not centralized SIP trunk as again with WAN failure it would not buy you much). 

[Andrew Skelly]

To add on to what Chris said, you can also configure SRST at each remote location, assuming your CUCM environment is centrally clustered and not a CUCM at each remote site.  This will allow 911 calls (as well as any other outbound call) to go out the local gateway/ISR via POTS or ISDN.