SRST Redundancy

[inhamit]

Hi, We have Branch office and Head office sites. At head office, we have Cisco CUCM application running and at the branch office, we have SRST router 1 and 2, both connected to head office over WAN. SRST router 1 should come in to picture when there is no connection to Cisco CUCM. When Cisco CUCM and SRST router 1 is offline from the network, SRST router 2 should take all internal calls and process. Please suggest, what configuration I should apply at CUCM and SRST router 1 and 2 side.

[Roger Kallberg]

AFAIK there is no redundancy for SRST.

[inhamit]

Thanks. So we cant have redundancy in SRST router 1 and 2. so If SRST router gone failed, calls will not work. Could you please provide the feasible solution for this?

[Roger Kallberg]

AFAIK there is no solution. SRST is to be used as a temporary option to provide basic telephony services in case that the connection with the primary service fails. Having a redundancy solution for the redundancy service isn’t a question I’ve ever came across or even discussed with anyone.

[inhamit]

So in our case, Router 1 at Branch office shall be configured as SRST router so when there is no connection to head office, Router 1 will process all the calls. If Router 1 and Head office CUCM is not available, then no calls will work in the branch office.

[inhamit]

@Roger Kallberg Could you please suggest me here as per above explanation?

[Roger Kallberg · Accepted solution]

I have not much more to add on this. You cannot have the SRST switch between two or more routers by an act of magic. If both the router 1 and the connection with the CM for whatever reason is in a none working state they yes there would be no call service at the branch.

[JamesHawkins · Accepted solution]

Like Roger redundancy for SRST is something I have never seen asked for but, if you really need this, you could look at using Cisco Embedded Event Manager to achieve it.

This would involve configuring the first router as an SRST gateway as per normal and then setting up the second router to monitor the availability of the first router - maybe through a dedicated VLAN - and if it loses connectivity run an EEM script that would no shut a subinterface on the second router which would have the SRST IP address on and then add the rest of the SRST config.

This would be very "bodgy" and I would not attempt it unless it was urgently needed and there were no other options.