Rstp Proposal Agreement Sequence


The port of SWB to SWA is the base port and refers an agreement to SWA. This begins the synchronization process in which (Just to emphasize a very important fact before going in the order of steps, note that the SWA port appears as a designated discarding, as it is the default port role and the default status in RSTP. Each designated discarding (and Designated Learning Learning) port sends BPDUs with the entire bit proposal. The SWB port will also appear as a designated discard and can also send suggestions, but it is not relevant at this stage, because after receiving a superior BPDU, the port role of SWB changes from SWA to root.) “If a designated port is in a state of rejection or learning (and only in this case), it fixes the bit of proposal on the BPDUs it issues.” When a switch receives a BPDU that fixes a bit of proposal on its root port, all non-Edge ports are put in a state of rejection… This process is called Sync. A sync switch is isolated from the network, so the loops cannot be run by the network. When a new connection is created between root and Switch 1, both ports are moved to a certain blocking state until they receive a BPDU of their equivalent. The proposal bit on BPDUs is only fixed and sent if a designated port is in a state of rejection or learning. This process occurs for port P0 of the main deck. As Switch 1 receives superior information, Switch 1 immediately knows that Port P1 is the new root port. Switch 1 then ensures that all ports are synchronized with this new information. – After the reciprocal exchange of BPDUs, which ultimately contain suggestions, each switch will be aware that the connection must remain blocked, because the base port on both switches will not be changed.

Therefore, after replacing the BPDUs on the S2-S3 connection, it will be immediately clear which port is the designated port and what is the alternative port on that connection. The alternative port no longer sends BPDUs and remains in a state of rejection, while the designated port slowly moves from rejection to “Learn” to redirect state. However, no agreement is sent from the two switches and no other non-edge port is blocked due to the receipt of a proposal. The proposal/agreement mechanism only applies to P2P duplex connections between two switching devices. If the proposal/agreement fails, a designated port is selected based on two forward delay intervals, such as the designated port choice in STP mode. 2.) Unlike animation, the proposal/agreement process between S2 and S3 does not take place at all. It is true that S2 can send a proposal to S3. However, S3 and S2 have already chosen another root port, and the arrival of BPDU on both sides will not change this selection. This means that the connection between S2 and S3 must be blocked, otherwise a loop would be formed to cross these two switches. On the other hand, a proposal/agreement procedure is used to quickly establish a link to a transit state. Therefore, even if s2 or S3 sends a proposal to its neighbor, no agreement can be sent, because the connection between S2 and S3 must remain blocked. whether this proposal and agreement will only take place after the choice of the root bridge or after the change in topology? Then SW3 sends an agreement so that SW4 and 0 can be retransmitted.

1.) The proposal/agreement process between S4 and S2 should be in the opposite direction. At present, it has been shown that S2 sends a proposal to S4 and S4 to respond with an agreement. It`s not true. A proposal can only be sent from a designated port in the discarding or learning state, as described in the Cisco document “Understanding Rapid Squeeze Tree Protocol” at SW2, sends a BPDU with a set of TC, since SW2 was considered root for a short time before SW2 heard a better BPDU from SW1. Then SW3 sends the BPDU agreement.


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