SRST Timer

Unanswered Question
Sep 29th, 2009

Hello Guru,

after MGCP fallback to SRST, what is the timer the SRST router back to CUCM? immediately? or some delay?

if it is immediately and if WAN link flaps, will the T1 D channel flap as well?

I have this problem too.
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Hythim Ali El Hadad Wed, 09/30/2009 - 07:15


Once the connection with the call manager is reestablished

the ip phones cancel their registeration to the SRST and reregister with the call manager

also could you plz show the 2nd ask in more details?


study_voip Wed, 09/30/2009 - 10:28

thx for the reply

the mgcp gateway will register back immediately after IP connectivity to CUCM servers restored

however, IP phones don't because the default 120 second

so during the 120 seconds, no outgoing calls via gateway, this is too bad

other thing, if the IP connectivity between CUCM and gateway are flapping, so the PRI D channels will be up/down, this is too bad as well

virverma Wed, 09/30/2009 - 10:27

If you plan to use the default time interval between keepalive messages, which is 30

seconds, you do not have to perform this task.



1. call-manager-fallback

2. keepalive seconds

3. exit

study_voip Wed, 09/30/2009 - 10:36


I am thinking we updated in same time, I did take a look the timer setup under call-manager-fallback, but it is for the communicate between SRST router and IP phones, not between SRST and CUCM

virverma Wed, 09/30/2009 - 10:57

SRST will take over after 3 incomplete ntfy messages are sent to the call manger from the router. this is not configurable.

study_voip Wed, 09/30/2009 - 11:06

can I ask the SRST router stay there for certain time before switch back to CUCM?

virverma Wed, 09/30/2009 - 16:42

sorry for late reply,

in cucm, in gateway configuration page there is option for

swithcback timing and swithcback uptime-delay

study_voip Thu, 10/01/2009 - 19:32

unfortunately, the way you introduced not working

I tried different combination, including config

ccm config

ccm config server

mgcp restart-delay

ccm switchback uptime-delay


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