Rapid Reconvergence

This section describes the RSTP rapid behavior following a topology change.

In this example, the bridge priorities are assigned based on the order of their alphabetical letters; bridge A has a higher priority than bridge F.

Suppose you have a network, as shown in Initial Network Configuration, with six bridges (bridge A through bridge F) where the following is true:

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Initial Network Configuration

The network reconverges in the following way:

If the link between bridge A and bridge F goes down, bridge F detects the root port is down. At this point, bridge F:

As shown in Down Link Detected, after the configuration update, bridge F:

As shown in New Root Bridge Selected, after the configuration update, bridge E:

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New Root Bridge Selected
As shown in Communicating New Root Bridge Status to Neighbors, when bridge F receives the superior BPDU and configuration update from bridge E, bridge F:
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Communicating New Root Bridge Status to Neighbors
Bridge D believes that bridge A is the root bridge. When bridge D receives the BPDU from bridge E on its alternate port, bridge D:

As shown in Sending a Propose Message to Confirm a Port Role, after the configuration update, bridge D:

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Sending a Propose Message to Confirm a Port Role
Upon receiving the proposal, bridge E (as shown in Communicating Port Status to Neighbors):

The existing designated port enters the blocking state.

Bridge E then sends:

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Communicating Port Status to Neighbors
To complete the topology change (as shown in Completing the Topology Change):
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Completing the Topology Change
Final Network Configuration displays the new topology.
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Final Network Configuration