from fwd to listening

daghighi.navid · ‎06-07-2007

Hi,

I am looking for a document on cisco.com (or other) which explains *in detail* when does a port transitions from forwarding into listening or from blocking into listening, for both STP and RSTP.

Thanks,

Navid

ycae · ‎06-07-2007

Here is a document for RSTP:

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml

This one could also help for STP.

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094797.shtml

But there are alos other documents available on cisco.com. Just use the Search function

Yves

daghighi.navid · ‎06-08-2007

Thanks Yves.

I did read these doc, but didn't find the exact answer to my question.

So I will try to give the answer myself : if somebody could correct me, I would appreciate.

For STP :

1/ A port will transition from BLOCKING into listening when mac_age expires:

a/ if it has not received any bpdu

b/ or if all bpdu received are inferior to the one it usually receives

2/ A DESIGNATED port will transition from forwarding into listening when mac_age expires :

a/ only if it receives a bpdu better than the one it usually sends out

3/ A ROOT port (called r) will transition from forwarding into listening when mac_age expires if :

a/ if it has not received any bpdu from the root switch

b/ or if any other port of this switch receives a bpdu superior to the one sent by the current root to this port (r)

Thanks,

Navid