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How to configure Cisco ISR 4321 as SRST

Level 1
Level 1

Hi to all!.


I have to configure a Cisco ISR 4321 Voice Gateway as SRST for a CUCM in a central Site.


This Router will handle a E1 and will be connected to Central PUB & SUB CUCM with SIP trunk.


Could you guide me to me how to configure this feature and all tips regarding that configuration please?


I configured Cisco Voice gateway between Asterisk PBX, but not yet with CUCM. 


Thanks in advance.


Kind Regards.


4 Replies 4

The 4000 series SRST configuration isn't really all that different than a 2900/3900.

You have to be running SRST 8.6 or higher, but if you have a current IOS you are fine there.

Check here for the Admin/Config guide:

License Part Numbers can be found here:

Dear Maren,


              Many thanks por your quick response.


I am confused about this options and I dont know if I have to use or don t:


Should I use this ?  srst mode autoprovision-none 

or should I use this? srst mode autoprovision all


Thanks in advance.


Kind Regards.


You want auto-provision all.


As the wording implies, this allows SRST to automatically provision phones that come to it for SRST services. If you use auto-provision none, you would have to manually pre-configure all phones that would require SRST services. That is used in an E-SRST environment, or if you are running CME in SRST mode so that you can pre-configure some or all phones with specific services and features during an SRST event.



I should mention there are additional considerations with regards to what information is saved in your running-config if you do a wr mem during or after an SRST event.


There is a longer discussion of this on:


Look at both the command-syntax section and the discussion further down the page.