HSRP and ISDN Backup

[c1sc0m4n]

Hi,

I have been given the challenge of setting up HSRP but need to know if I can configure ISDN backup with HSRP. Let me explain: -

I have 2 sites and have a Leased Line between the two and Backup ISDN for that line (on a separate box). I also have 2 x 2600 Series Routers and need to run HSRP between them.

My question is: - Can I perform HSRP between them and still run ISDN backup- i.e. HSRP with ISDN Backup. This is because obviously you have 2 separate boxes - one for the LL and one for the ISDN Backup - how could this be done??

Please help!

 

[routerman]

Yes you can do this.

HSRP sets a virtual gateway IP and MAC address, shared between 2 or more routers. One is a Primary, when the secondary stops receiving HSRP hellos from its HSRP neighbour it becomes the master.

So what you need to do is make the LL router HSRP master, and configure it to track the LL. You set it to reduce its priority when the LL fails, so the ISDN becomes the HSRP master. Packets then flow to the ISDN router, which brings up its link and away you go.

If you dont use the tracking option then the LL router will need to be able to send packets to the ISDN when its LL fails.

 

[c1sc0m4n]

Hi mate - thanks for that - I understand exactly what you mean but I have one more question mate - If the LL Router reduces its priority - when the LL (or serial interface) comes back up, will the priority of the LL router increment back to become the active router?

Thanks for the super prompt reply - very appreciated

 

[routerman]

yes, that's also possible you use the standby preempt command. You have to add the command to make it switch back, otherwise the backup kicks in and stays in even when the LL comes active again.