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Effect of CDP on HSRP



There are two Edge routers (ER1 and ER2) which are connected to a ISP R1 router. Both customer end routers are connected in a switch  ESW1. ER1 and ER2 are running HSRP in order to avoid single gateway failure. CDP is disabled in HSRP interfaces. Strange thing is that ERI Fast ethernet have some problem but line protocol is not showing down. So Fail over is not happening to ER2. So User cant reach to ISP IP. 

Apart from shut no shut from ER1 interface what all other ways are possible to failover from ER1 to ER2 inorder to reach ISP IP. Is it because of "CDP issue". Because my suspect is CDP works at Layer 2. As CDP is blocked thatswhy it is not propagating the CDP information to connected interface. You may assume there is not any routing issue in between. HSRP configuration is shown in the diagram. Could you please provide me some valuable commencts on it.




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I have several comments to

I have several comments to offer about your situation.

- I do not see any way that CDP being turned off is having any impact on your HSRP.

- I do not understand why CDP is turned off on this interface. I can understand not running CDP on the interface connecting to the ISP. But this is the interface to your inside network. So why not run CDP?

- Why are you doing track FA0/1 when FA0/1 is the interface with HSRP? You would typically track the interface connecting to the ISP. The HSRP packets being transmitted should be sufficient to detect if there were problems with FA0/1 between the routers.

- If you set the priority of ER1 to 150 and the priority of ER2 is 100, then even if track worked it would lower the priority by 10 and you still would not fail over.

- Your drawing does not show how you connect to the ISP. That might or might not be part of the issue you are experiencing.

- If you want to track then I might suggest setting up IP SLA to track access to some IP address inside the ISP and use that to trigger failover between HSRP routers.





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