HSRP over three interface but two routers

[denny_zulkasi]

Hi, I have Router A which is a 1720 with a Serial and BRI interface and I also have Router B which is a 1720 with ISDN interface.The serial in router A is connected to the leased line and is a primary line to connect to the FR network. The BRI in Router A is configured as a backup interface in case of a failure with the leased line the BRI supposed to dial to the FR provider's AS. My boss also wants to utilize Router B as a standby router to connect to the Internet in case of failures in both interface in router A. The only way I can think of is using HSRP, but I'm not sure which interface on router A that I should track because if I track the S0, the HSRP will make the router B to fire up and disregard the ISDN interface in Router A. Therefore if I track the BRI on router A, HSRP will always elect Router B as the active router since the BRI is down because it is configured as back up interface. Is there anyway I can meet the situation where the three interfaces backing up each other with or without HSRP ?

Thanks and Best Regards

[steven-dunn]

Tracking an interface only reduces the priority of HSRP. I would track the serial interface on Router A. If it dies Router B should take the default gateway and call into the SP cloud. I would then track the BRI on router B to demote it further than router A should it fail. It's messy but it works.