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Extension Mobility service on Subscribers ?

I have 2 servers in my CM cluster, a Publisher and a Subscriber. I have been told that the Extension Mobility service can only run on the Publisher, meaning this facility is not available (no one can chage their extension mobility state) in the event of the Publisher becoming unavailable. This certainly seems to support what I have just read :

"If the system is running but the publisher is not available, the following operations will not be available:

•Configuration changes

•Call forwarding changes

•Extension Mobility login or logout operations

Extension Mobility will not function without the publisher because it requires access to the read/write database. Therefore, Cisco recommends running this service on the publisher only."

When I check the details of the Extension Mobility service, I find the service URL contains the IP Address of the Publisher. When I look in Service Activation, the Extension Mobility service is enabled on both the Publisher and the Subscriber.

My questions are :

1) Is it still the recommendation that Extension Mobility service is only run on the Publisher ? It seems as though the service would never be used on the Subsbriber anyway as there is no reference to that server in the service URL, is that correct ?

2) It was my understanding that if the publisher was not available, you could make Call Forwarding changes, but they would not be preserved once the Publisher was brought back up - is this not the case (as the extract above suggests) ?

3) Is there any benefit in creating a second service "Extension Mobility Backup" etc. and pointing the service URL to the subscriber running the Extension Mobility service ? with the caveat that these changes would be lost when the publisher comes back up ? (I guess not given the extract above).

Has anything changed in this area ?


Re: Extension Mobility service on Subscribers ?


to answer your questions:

1. You can install the extension mobility service on the Subscriber servers, but remember, the IP Phone Service "Extension Mobility" URL can only point to one server at a time and I cannot imagine a situation when there are two services on the ip phone, both Extension Mobility, saying something like "Extension Mobility 1" and "Extension Mobility 2" and the the IT manager would announce if the first is not working, use the another.

2. You cannot do any configuration changes while the Publisher server is down, since the replicaton always goes the Publisher -> Subscriber way and never vice versa. Of course, you can use /ccmadmin on the subscriber servers, but it will update the Publisher's database.

"The message Database Unreachable is displayed on the IP phone (7960 or 7940) when the subscriber CallManager has Structured Query Language (SQL) connection or replication problems with the publisher CallManager." This is what Cisco says at

3. No.

You can, however, do some experimenting with the Extension mobility service which comes in the Cisco IP Phone SDK. If you want to play with Java.