CME as SRST configuration

Unanswered Question
Nov 5th, 2008

We are using CME as SRST for our remote site How does CME get the phone configuration from Call Manager. If I change a dn on Call manager, the old DN is still present on the phone in SRST. Seems that CME keeps the old configuration of the phone ans ignore the changes made to Call manager.

Thanks

I have this problem too.
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Tim Smith Wed, 11/05/2008 - 13:56

Hi Richard,

CME-SRST mode does not have any method for keeping changes synced from CallManager. CallManager does not communicate config info directly to CME-SRST routers.

Might be best to post your config.

CME-SRST gets the config from the phone when it first registers with the CME-SRST router, i.e. on the first wan link failure.

You would usually set up CME-SRST not to save the phone MAC addresses. This way you dont have to keep the CME / CCM config in sync. CME-SRST will just get the latest config from the phone each time it fails over.

You can however configure specific features for specific phones by using their DN.

Also, are you saying you change the DN in CallManager while the phone is in SRST mode?

There may be a 3rd party product for syncing CME-SRST and CallManager though.

Cheers,

Tim

allan.thomas Wed, 11/05/2008 - 15:01

You should configure 'srst mode auto-provision none' under the telephone-service, instead of either 'all' or 'dn'.

This ensures that the learned ephone-dns do not appear in the running configuration and then subsequently written to nvram.

Therefore when ever you change your DN within CUCM, this will be the DN on the phone when SRST occurs.

'srst mode auto-provision none' is particularly useful if you are using pre-built ephones and ephone-dns.

HTH

Allan.

richard.leclerc Thu, 11/06/2008 - 06:15

I am using auto-provision set to all since I have phones with BLF and I want to have the BLF as well in SRST. Do you have a trick on how to have BLF and auto-provision set to none?

Thanks for the reply

Richard

allan.thomas Thu, 11/06/2008 - 06:43

Hi Richard, unfortunately this is the dilema, and not the answer you are looking for? :-(

The issue with auto-provision all as you have mentioned is that the ephone and ephone-dn configuration is written to the running-config and will be retained for all subsequent SRST failovers.

So if the DN configuration is changed in CUCM, this will not be updated when the phone re-registers in SRST again. The previous provisioned configuration takes precedent. Unless the router is reloaded of course.

The alternative is to configure 'auto-provision none', and then pre-build your ephone-dn configurations, the downside is that you will have to manually change them if the DN information changes.

At the end of the day SRST redundancy should only be there as a temporary measure until which time the WAN or CUCM is restored to service.

This obviously depends on the expectation set to the users. Otherwise you will be in the situation where administration will become too time consuming.

Allan.

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