Synchronization Of Port Roles - Cisco Catalyst 2960-XR Configuration Manual

Configuring Multiple Spanning-Tree Protocol
Figure 8: Proposal and Agreement Handshaking for Rapid Convergence

Synchronization of Port Roles

When the switch receives a proposal message on one of its ports and that port is selected as the new root port,
the RSTP forces all other ports to synchronize with the new root information.
The switch is synchronized with superior root information received on the root port if all other ports are
synchronized. An individual port on the switch is synchronized if
• That port is in the blocking state.
• It is an edge port (a port configured to be at the edge of the network).
If a designated port is in the forwarding state and is not configured as an edge port, it transitions to the blocking
state when the RSTP forces it to synchronize with new root information. In general, when the RSTP forces a
port to synchronize with root information and the port does not satisfy any of the above conditions, its port
state is set to blocking.
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Catalyst 2960-XR Switch Layer 2 Configuration Guide, Cisco IOS Release 15.0(2)EX1
RSTP Overview
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