Port Roles
RSTP uses information from BPDUs to assign port roles for each LAN segment. Port roles are not user-configurable. Port role assignments are determined based on the following criteria:
- A unique bridge identifier (MAC address) associated with each bridge
- The path cost associated with each bridge port
- A port identifier associated with each bridge port
RSTP assigns one of the following port roles to bridge ports in the network, as described in the following table.
RSTP Port Roles
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When RSTP stabilizes:
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All root ports and designated ports are in the forwarding state.
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All alternate ports and backup ports are in the blocking state.
RSTP makes the distinction between the alternate and backup port roles to describe the rapid transition of the alternate port to the forwarding state if the root port fails.
To prevent a port from becoming an alternate or backup port, use the command:
configure stpd stpd_name ports active-role enable port .
To revert to the default that allows a port to be elected to any STP port role, use the command:
configure stpd stpd_name ports active-role disable port
To view the active-role status, use the command: show stpd ports.