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New Member

SRST and dialing off-site extensions

We have a hq and a branch office with a CallManager located at hq. In event of a WAN failure, with SRST will the branch office users be able to reach hq extension numbers by continuing to dial just the internal extension numbers, or is it necessary to dial the complete phone numbers?

Many thanks for you help


Hall of Fame Super Red

Re: SRST and dialing off-site extensions

Hi Mark,

It is possible to configure SRST to support internal dialing (example 4 digit internal numbers). Here is an excerpt from a really excellent new Interactive Cisco doc that has sample configs etc. for your SRST setup;

Ensure 4-Digit Dialing to Head Office is Maintained

In order to maintain 4-digit dialing for your users to reach the head office during SRST failover, you must configure additional dial peers as shown in this output:


voice translation-rule 1 !--- Appends 14085015 to any called number starting with 5

rule 1 /^5/ /14085015/



voice translation-profile toHQ

translate called 1

dial-peer voice 5000 pots !--- Maintains 4-digit dialing to head office

translation-profile outgoing toHQ

destination-pattern 5...

port 1/0:23


From this excellent new Interactive doc;

Unified SRST Interactive Voice Network Configuration Example

Hope this helps!


New Member

Re: SRST and dialing off-site extensions

Dear Rob,

The calling from Remote Site(SRST) to HQ we can do by using dial-peer and translation patterns.

But From HQ to remote site ,how is it possible becos the phones are unregisyered fro the ccm.

Please give me some idea




Re: SRST and dialing off-site extensions

to dial fro HQ to remote site you only have to set in CUCM under the directory number configuration of the line the value

"Forward Unregistered Internal" to the remote site external phone number. now, in SRST mode when the users at HQ dial the extension number of a remote sites employee the call is automatically routed over PSTN!

VIP Super Bronze

Re: SRST and dialing off-site extensions

If you have CM 4.2 or 6.X you can configure "forward on unregistered" settings on the DNs and inculde the full DID there, so if the remote site is in SRST mode the phones appear unregistered in CM and will follow this route, which will be xparent to the end user, because they will just dial the normal extension

If you have CM 4.1 or eariler or 5.X there is nothing you can do as after dialing the internal Extension CM will fail to route it and will folllow the "forwaed busy" route set on the phone which most liekly is VM.

The only thing you can do is to dial the full DDI



Please rate all useful posts "The essence of christianity is not the enthronement but the obliteration of self --William Barclay"

Re: SRST and dialing off-site extensions


By default, the full number will have to be dialed. However, you can configure it to work with just the extension.

Let's say you have 4 digit extensions that begin with 6. The full phone number is 1112226... your users are used to just dialing 6... to reach HQ. If you enter this command:

num-exp 6... 1112226...

When your users dial for instance 6123, it will be automatically expanded to 1112226123 (note that if you need a leading 9 in your dial plan, you would need to include that in the num-exp command) and sent over the PSTN transparently to the user.

Hope this helps, remember to rate helpful posts!



VIP Super Bronze

Re: SRST and dialing off-site extensions


I am not sure if this will work.

This guys have CCM in their HQ.

Number expansion only works on the Voice gateway, hence for this to work, they will have to configure all their 4 digit extensions as RP pointing to the gateway.

The problem is CCM will not allow this because it will complain that the patten already exist.

Please rate all useful posts "The essence of christianity is not the enthronement but the obliteration of self --William Barclay"