Chapter 17
| Spanning Tree Commands
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Command Mode
Interface Configuration (Ethernet, Port Channel)
Command Usage
◆
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.
Example
Console(config)#interface ethernet 1/5
Console(config-if)#spanning-tree edge-port
Console(config-if)#spanning-tree root-guard
Console(config-if)#
spanning-tree
spanning-disabled
This command disables the spanning tree algorithm for the specified interface.
Use the
no
form to re-enable the spanning tree algorithm for the specified
interface.
Syntax
[
no
]
spanning-tree spanning-disabled
Default Setting
Enabled
Command Mode
Interface Configuration (Ethernet, Port Channel)
Command Usage
When spanning tree is enabled globally (
command) or enabled
on an interface by this command, loopback detection is disabled.
