Trunking and Hsrp

[asegun]

I am running hsrp on two cisco 3640 routers, which a connected to a cat 4006 running Cisco ios. On the cisco 3640s I am trunking because I have sub interfaces. Once I active hsrp, the routers start flapping. But is I run hsrp on the physical interfaces without trunking(obviously), Hsrp works fine

[Prashanth Krishnappa]

There might be some misconfiguration. Follow the steps in the following page

http://www.cisco.com/warp/public/473/62.shtml

If it still happens, I suggest that you open a TAC case

[rfroom]

There are some issues with spanning-tree and ethernet controller on the 3640. Two quick fixes would be to upgrade to the 3640 to the latest 12.2 train or configure trunk-fast on the 4006 (7.2.x code)