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SIP-E1-SIP Path monitoring from CUCM or ISRg3

Hello Colleagues,


I had an interesting request, hope you would be interested as well.


For some historical reasons we had the following infrastructure:


Phone <-> CUCM <-> SIP trunk 1 <-> ISRg3 N1 <-> E1 PRI <-> ISP voice gateway N1 <-> SIP trunk 3<-> PSTN

Phone <-> CUCM <-> SIP trunk 2 <-> ISRg3 N2 <-> E1 PRI <-> ISP voice gateway N2 <-> SIP trunk 4<-> PSTN


In normal state both ISRg3 and ISP gateways serve outbound calls in round robin fashion.

I fully understand how to process with E1 and ISP gateways crashes but I would like to know if there is a way for CUCM to understand that SIP trunk 3 or SIP trunk 4 fails and not to route calls  to corresponding SIP trunk 1 or SIP trunk 2.

For example, can we somehow pass through the network the 503 or 404 SIP responses from SIP trunk 3/4 connected devices. In this case, if I understand things right,  I would be able to make  CUCM to start the rerouting process to another SIP trunk or Route group.


Long story short, CUCM is connected to PSTN over two different paths. Is there is an option to reroute outbound call between these paths depending on the call state received over the SIP-E1-SIP chain?


Best regards,




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