Survivable Remote Site Telephony (SRST) is a feature used in cisco IPT deployment to provide fallback in case the Remote site looses connectivity with the CUCM cluster .
The local voice gateway based on cisco IOS has the feature of providing local call agent functionality once the gateway/remote site phones looses connectivity with the CUCM .
We can deploy SRST based on different protocol (MGCP,h323 and SIP).
The MGCP fallback uses h323 configuration as a default protocol
Also there are various mode of deployment of srst like with CME as SRST or normal SRST .
Here are the various options for deployment of SRST .
1. Call-Manager-Fallback : This option is used basic deployment of SRST and have very limited feature to use. Also the use is very limited.The config of the phone are fetched using SNAP from the Phone itself
2. Telephony-service with auto provision none : This option uses the CME router as SRST and if we used the telephony-service option with auto provision as none in that case the snap discovered the phone config and store the phone config in the ios running config .However the ephone-dn and ephone config is not visible in the router running config and hence customization cann't be done .
3. Telephony-service with auto provison dn : This is same as "Telephony-service with auto provision none " only difference is that in this case the ephone-dn is visible in the route running config .
4. telephony-service with auto provision all : This is same as point number 2 and only difference is in this deployment both the ephone and ephone-dn is visible in the route ios running config .This method has more flexibility as the ephone and ephone-dn can be modified and also support maximum feature
Note : if you are using extension mobility with SRST then EM login will not work ,hence any new EM login will not be successful however existing login phone will continue to work
The local voice gateway based on cisco IOS has the feature of providing local call agent functionality once the gateway/remote site phones looses connectivity with the CUCM .
We can deploy SRST based on different protocol (MGCP,h323 and SIP).
The MGCP fallback uses h323 configuration as a default protocol
Also there are various mode of deployment of srst like with CME as SRST or normal SRST .
Here are the various options for deployment of SRST .
1. Call-Manager-Fallback : This option is used basic deployment of SRST and have very limited feature to use. Also the use is very limited.The config of the phone are fetched using SNAP from the Phone itself
2. Telephony-service with auto provision none : This option uses the CME router as SRST and if we used the telephony-service option with auto provision as none in that case the snap discovered the phone config and store the phone config in the ios running config .However the ephone-dn and ephone config is not visible in the router running config and hence customization cann't be done .
3. Telephony-service with auto provison dn : This is same as "Telephony-service with auto provision none " only difference is that in this case the ephone-dn is visible in the route running config .
4. telephony-service with auto provision all : This is same as point number 2 and only difference is in this deployment both the ephone and ephone-dn is visible in the route ios running config .This method has more flexibility as the ephone and ephone-dn can be modified and also support maximum feature
Note : if you are using extension mobility with SRST then EM login will not work ,hence any new EM login will not be successful however existing login phone will continue to work
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