very good explanation on rstp. I have my doubts. Is the question of whether the choice of root bridge (proposal and agreement) takes place in parallel between each switch, as you explained in order, a little confusing. For example, between sw1-sw2 and sw3-sw4 occur in parallel? The order of the steps is not entirely accurate. Rightly so, it should follow this sequence: I explained it one after the other, because it would be very chaotic to explain poV at once by all the switches. When a designated fault sport does not get an agreement after a proposal is submitted, it slowly switches to the redirect state and builds on the traditional 802.1D list learning sequence. This can occur if the remote bridge does not include the RSTP-BPDUs or if the remote bridge port is blocked. (To emphasize a very important fact before entering the sequence of steps, remember that the SWA port is displayed as a designed discarding, as this is the default port and port state in RSTP. Each designated learning (and designated learning) discarding door sends BPDUs with the Bit Proposal. The SWB port is also considered a designed discarding and can also send proposals, but it is not relevant at this point, as the swB port role changes after receiving a higher BPDU from SWA to root.) On the link between S4 and S2, the fa0/2 of the S4 is the designated port, while the Fa0/2 of the S2 is the root port, so the S2 cannot send suggestions about this connection. The correct sequence of events is therefore that the S4 sends a proposal to the S2 and responds with S4`s agreement after blocking all its non-edge ports. Thank you.

I had to read it twice to be clear. Even the INE document is not very clear about this Once p0 gets this agreement, it can immediately switch to the redirect state. This is step 4 in the previous figure. Note that the p3 port remains in a certain state of failure after synchronization. In step 4, this port is in exactly the same situation as port p0 in step 1. He then begins to make a proposal to his neighbor and tries to quickly move to the state of transmission. . Все свичи шлют bpDU в сооответствиии с hello-таймером (2 секунды по умолчанию) – обрасывание (discarding), замееяеннтabled, blocking и listening – learning – forwarding Configure the Dynamic Path Cost in an Aggregate Port Maybe then SW3 gets a better BPDU via SW2, SW3 would then synchronize with SW2, while blocking its downward port to SW4, and once it is done, would then synchronize it with SW4. Yes, you`re right, I missed the video again, yes, you need to change this animated video a bit, as you suggested.

Cisco has introduced an extension of the synchronization mechanism that allows a bridge to only put its old root port in a state of fault during synchronization. The details of how this mechanism works go beyond the scope of this document. .