hi! I've a stack of 4 cisco3524(IOS) switches with 2 of these switches (the bottom and the top) connected to the 2 core switches (6509-CatOS) by fiber link.

I noticed that both of these interfaces connected to the core switches are in forwarding state. I would like to have one of them as a standby and not forwarding traffic for both. The reason is because i noticed that one of the link is not that stable, there are intermittent packet lost. So, i would like all the traffic to go to the other fiber link and the one with problem as standby.

What need to be done to achieve this? Btw how do i check whether the link with intermittent problem is it caused by the hardware or something else. From the interface it will show link and protocol up, but when i do a continous ping to other devices outside of the 4 edge switches, there's intermittent timeout.

Please advise. Thanks.