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HSRP with ISDN Routers


At the central site I have two 2620 routers (Router A and B) with a ISDN BRI interface and share a single ISDN BRI line (both connected and active)and a single telephone number. I want these to act as active/standby using HSRP and whichever is the active router should respond to all incoming ISDN calls. At each remote site (e.g. Router C) I have a 1720 configured for DDR to the central site.

RouterA(2620)|---|ISDN BRI0:1| |ISDN BRI|---Router C

RouterB(2620)|---|ISDN BRI0:2|

I need both router and link redundancy at the central site. Configuring HSRP and tracking the BRI0 interface is straightforward. However, cant find a way to enforce router A, configured as the HSRP active router, to be the one to pickup all ISDN calls received on the shared ISDN BRI. The standby Router B should only respond to incoming ISDN calls (i.e. answer the call) when it becomes the active router (i.e. when Router A is down or its BRI0 interface is down).

What seems to happen in practice is that the fastest router always handles all incoming ISDN calls. Is there a priority mechanism available? Has anyone done this kind of thing before?

Thanks in advance,



Re: HSRP with ISDN Routers

Often times complex configuration issues are best addressed in an interactive session with one of our trained technical assistance engineers. While other forum users may be able to help, it’s often difficult to do so for this type of issue.

To utilize the resources at our Technical Assistance Center, please visit and to open a case with one of our TAC engineers, visit

If anyone else in the forum has some advice, please reply to this thread.

Thank you for posting.

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