Spanning-tree loop caused WAN to be unreachable(?)

[Little Bunny]

We had an issue at a site with symptoms suggesting the site was hard down, couldn't reach the router or anything on the LAN. However the root cause turned out to be a Layer 2 loop on the LAN. During the issue the router WAN interface was unreachable, is this normal?

Thanks

[Jon Marshall]

Unreachable from where, within the network or remotely ?

But a general answer to your question is yes an STP loop could indeed tie up the router as well. If the LAN interface of the router was receiving broadcast caused by the STP loop the router could indeed be too busy to handle any other requests.

Jon

[Little Bunny]

Thanks Jon, that makes sense. It was unreachable remotely.

Amy

[manju.cisco]

Hi,

What Jon said must be true, bcoz of huge broadcasts router cpu utilisation was full i believe and had no time to recevie your ping (echo) request and also to reply

Loop always screws one's life

By the way, did you see your WAN link down at that time if it was a serial link ?

Thanks,

Manjunath