SRST doesnt work with CCM4.3 AND IP PHONES 7945 &7941

Unanswered Question
May 12th, 2008


i have a CCM 4.3(1) working with 7945 and 7941 ip phones working, and a 2851 router with SRST, but when i see the ip phones supported by the SRST router, i only see other phones different. i have already configured the SRST but i does not work, does anyone know how to solve the problem?

I have this problem too.
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giovanni.cock Thu, 05/15/2008 - 16:06

hi, thanks a lot for your answer, but i have alreday checked all these points. i send you more information about the TOip solution that i am working in.

do they all have the SRST reference?

a/yes they do.

do you have all the proper routing to reach the SRST?

a/the SRST router is the same voip gateway (pstn connections)

are they on the same vlan as working phones?

a/ the router is on the same vlan where the CCM is working in.

do you have the required SRST version and firmware loads?

these are the firmware:

COBOG-2851-VG1#sh call-manager-fallback

CONFIG (Version=4.1(0))


Version 4.1(0)

system message primary Sistema de Respaldo Activado

system message secondary Sistema de Respaldo

Limit number of DNs per phone:

7910: 36

7935: 36

7936: 36

7940: 36

7960: 36

7970: 36

Log (table parameters):

max-size: 150

retain-timer: 15

why i dont see the 7941 and 7945???

the router IOS is


and the ip phones firmware are:

7941 SCCP41.8-3-3SR2S

7945 SCCP45.8-3-3SR2S

these are higher that the document recomends, so i suposed that firmware version will work.

the CCM Version is, 4.3(2)

thanks a lot!


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