STP 5-rapid STP and Rapid PVST (fast spanning Tree protocol)

RSTP = 802.1w

Note The main points:

• Fast convergence is based on switch-related process synchronization

To open a command:

-Spanning Tree mode MST

-Spanning Tree mode Rapid-pvst

• The synchronization process only occurs on the peer & Non-edge port (the full Duplex,non-edge to have the Bpdu,edge port configured portfast command)

Note: If Portfast is not configured on the edge port and the port is full duplex, the host does not reply to agree when it receives the rapid STP proposal, so that the port automatically drops back to normal STP or pvst. We don't get the fast convergence effect. Rapid STP is turned on by default in MST, but if Portfast is not configured on the edge port, it will pass through the normal STP process.

-Spanning-tree Link-type "point-to-point | Shared

-Spanning-tree Portfast

• BPDUs of RSTP BPDUs and STP can exist simultaneously (RSTP BPDUs are v2)

-RSTP is backwards compatible with 802.1d BPDUs (run STP on RSTP devices not supported)

-Each switch in the RSTP sends a BPDU packet to the neighbor, the interval is hello interval (default 2s) and STP switches to wait for the root bridge BPDUs and then forward

-The neighbor switch in the RSTP topology is not received as a connection disconnect (equivalent to 6s, but Max age is 20s in STP)

• RSTP Several steps of the synchronization process (translated Cisco documentation)

1. If the proposal ' sender has a superior bpdus, the local switch realizes that sender
Should be the designated switch (have the designated port) and that its own port
Must become the new root port.

If the switch sending the request has superior BPDUs, the local switch will identify the sender as the designated switch (with designated port). Local switch's own port is set to root port

2. Before the switch agrees to anything, it must synchronize itself with the topology.

Before agreeing to any request, the exchange opportunity synchronizes with the existing topology (Root bridge, root port, all data match)

3. All Nonedge ports Imme diately is moved into the discarding (blocking)
No bridging loops can form.

All non-boundary ports (non-direct-attached hosts) go directly into the discarding state to ensure that no loops are generated

4. An agreement message (a configuration BPDUs) is sent-back to the sender, indicating
The switch is in agreement with the new designated port choice. This also tells the
Sender, the switch is in the process of synchronizing itself.

Then, the consent information (a configured BPDU packet) is sent back to the sender, telling the other switch to locally agree to choose your port as the new designated port. At the same time, this also means that the local switch is synchronizing with the topology

5. The root port immediately is moved to the Forwarding state. The sender ' s port also
Immediately can begin forwarding.

The root port is then immediately converted to forwarding state. The port of the sender switch can also start sending and receiving.

6. For each Nonedge port, currently in the discarding state, a proposal message is
Sent to the respective neighbor.

For the non-boundary port of the local switch, itself in the discarding state, the request information is sent to their connected neighbors.

(The following and so on)
7. An agreement message was expected and received from a neighbor on a nonedge port.
8. The Nonedge port immediately is moved to the Forwarding state.