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SRST fallback - service interruption


Good day,


We have a remote branch with 200 IP phone users and a voice GW with analog lines(FXO ports). Users receive & make calls through the voice GW 2911.

We need to setuo a new SRST router 2951. After setting up and while testing SRST fallback, we get "service interruption" msg on all the ip phones.

Find the attached config of the SRST router. Any config to be added in the router?.


SRST Reference created.

Device pool is mapped with the reference.

Note: Also send me the config how to make outgoing calls through analog ports of another voice GW during fallback...

SRST router: 2951

Voice GW: 2911

VIP Gold

Are those phones configured

Are those phones configured as SIP or SCCP in cucm? And are you able to see srst reference IP in IP Phones (Settings -> Device Configuration -> CM Configurations) ?

To route  all calls to another gateway you can configure a dial-peer.


Dear Suresh,90% of the phones

Dear Suresh,

90% of the phones are configured as SCCP & 10 % is SIP.

Models are 7911, 7942 & 7962, 6921 (SCCP) and 9971 (SIP). 

We didnt check the SRST reference IP durinf fallback. Will check & update.

We also will try the dial peer config from the router.for outgoing.

How to configure Incoming.

Current scenario: Incoming calls hits on the dial-peer and AA is played from the ISM module of the VGW 2911.

How to divert the incoming calls during WAN outage?



VIP Gold

I think you can create 2 more

I think you can create 2 more dial-peers in the same way, that you configured currently but with preference 1 as below..

dial-peer voice 2003 voip
preference 1 
destination-pattern ....
 session target ipv4:
 voice-class codec 2  
 dtmf-relay h245-alphanumeric
 no vad
dial-peer voice 2004 voip
 preference 1
 destination-pattern 2...
 session target ipv4:
 voice-class codec 2  
 no vad

Even though you can troubleshoot this call routing using 'debug voip ccapi inout' once phones get registered to srst router.

For SIP phones you need to configure 'voice register global' & voice register pools in 2951.


 Dear Suresh, Tnx for your


Dear Suresh,


Tnx for your suggestion. We will do this testing during non working hours and let you know the status...




Hi,IP Phone model 7911, 7942


IP Phone model 7911, 7942 are working in SRST mode but 6921 still it shows "service interruption"

We are unable to configure "voice register pools" as the tag number (1-250) following the command is not accepting in the router.



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