CODEWITHSUNDEEP
linux-kernelstp
John
John

Reputation: 3520

Preventing loop in STP on unreliable connection

I think I found a way that a loop can exist in STP, and I'm wondering if there are any known solutions to this.

:    +----- wifi -----+
:   PC1              PC2
:    +----- eth ------+

I have PC1 and PC2 connected via both eth and wifi, such that eth is the Designated Port, and wifi is blocked. Now say there were some over-the-air interference for wifi for 20s to the point where PC1.wifi does not receive a bpdu from PC2.wifi. (Note that neither PC1 nor PC2 know about the interference -- as far as they are concerned, wifi is still up). PC1 will assume that PC2 is no longer connected via wifi, and will set that port to a designated port, and bring it to a forwarding state. Once all of this happens, a multicast packet is received on PC1 via eth. Right at that moment, the wireless noise dies down, and PC1 is able to forward the packet to PC2 via wireless. P2 then forwards the packet to PC1 over eth, and so on and so forth, killing the entire system.

Is there any known way to prevent this? (Note: I am using the built-in linux STP from 3.4).

Upvotes: 1

Views: 125

Answers (0)

Related Questions