STP Questions

Ferret999

Hi all,

I have been reading through the BCMSN study guide which I must say I find a much better book than the BCMSN self study guide which seemed all over the place. Anyhow that is beside the point.

I want to check that I have this right if you have BPDU filtering enabled on a Portfast interface then you connect another switch to that interface the interface will remain in the forwarding state and a bridging loop might result because BPDU filtering is ignoring all the BPDU's is this right?

Also when you have two interfaces in a Etherchannel then STP sees them as one interface but can you tell which physical interface is actually forwarding the BPDU's or are the BPDU's that are sent also load balanced over all the interfaces in the channel?

Thanks in advance

dtlokee

Ferret999 wrote:

Hi all,

I have been reading through the BCMSN study guide which I must say I find a much better book than the BCMSN self study guide which seemed all over the place. Anyhow that is beside the point.

I want to check that I have this right if you have BPDU filtering enabled on a Portfast interface then you connect another switch to that interface the interface will remain in the forwarding state and a bridging loop might result because BPDU filtering is ignoring all the BPDU's is this right?

yes

Ferret999 wrote:

Also when you have two interfaces in a Etherchannel then STP sees them as one interface but can you tell which physical interface is actually forwarding the BPDU's or are the BPDU's that are sent also load balanced over all the interfaces in the channel?

Thanks in advance

In theory it does not matter which physical interface they are sent over, the Etherchannel bundle it treated as a single logical interface and all member interfaces have the same STP role as the port channel interface. If one interface were to go offline, the remaining interafces in the bundle would take the load (and the BPDUs)