Spanning-Tree Root-Guard - Edge-Core ECS4810-12M Layer 2 Management Manual

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This command defines the priority for the use of a port in the Spanning

Tree Algorithm. If the path cost for all ports on a switch are the same,

the port with the highest priority (that is, lowest value) will be

configured as an active link in the spanning tree.

Where more than one port is assigned the highest priority, the port with

lowest numeric identifier will be enabled.

Console(config)#interface ethernet 1/5

Console(config-if)#spanning-tree port-priority 0

spanning-tree cost (1053)

This command prevents a designated port

spanning-tree

into account and allowing a new STP root port to be elected. Use the no

form to disable this feature.

[no] spanning-tree root-guard

Interface Configuration (Ethernet, Port Channel)

A bridge with a lower bridge identifier (or same identifier and lower

MAC address) can take over as the root bridge at any time.

When Root Guard is enabled, and the switch receives a superior BPDU

on this port, it is set to the Discarding state until it stops receiving

superior BPDUs for a fixed recovery period. While in the discarding

state, no traffic is forwarded across the port.

Root Guard can be used to ensure that the root bridge is not formed at

a suboptimal location. Root Guard should be enabled on any designated

port connected to low-speed bridges which could potentially overload a

slower link by taking over as the root port and forming a new spanning

tree topology. It could also be used to form a border around part of the

network where the root bridge is allowed.

When spanning tree is initialized globally on the switch or on an

interface, the switch will wait for 20 seconds to ensure that the

spanning tree has converged before enabling Root Guard.

23. See Port Role under

"Displaying Interface Settings for STA" on page

| Spanning Tree Commands

from taking superior BPDUs

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