Spanning Tree Introduction: STP, RSTP, MSTP
©2008 Allied Telesis Inc. All rights reserved.
18.6
AlliedWare Plus
TM
Operating System Software Reference C613-50003-00 REV E
Software Version 5.2.1
Configuring STP
By default, RSTP is enabled on all switch ports. This section provides a procedure for
configuring STP (
Table 18-3
).
To configure other modes, see
“Configuring RSTP” on page 18.8
or
“Configuring MSTP” on
page 18.18
.
Table 18-3: Configuration procedure for STP
Advanced
configuration:
For most networks the default settings for path costs will be suitable, however, you can
configure them if required (
spanning-tree path-cost
).
Command
Description
RSTP is enabled by default with default settings on all switch ports to prevent layer 2 loops in your network.
awplus#
configure terminal
Enter Configuration mode.
awplus(config)#
spanning-tree mode
stp
By default, the device is in RSTP mode. Change to
STP mode.
awplus(config)#
spanning-tree {stp|rstp|mstp} enable
By default, spanning tree is enabled on all switch
ports. If it has been disabled, enable it for STP.
awplus(config)#
spanning-tree priority <priority>
By default, all devices have the same root bridge
priority, 32768 (8000 in hexadecimal), so the
device with the lowest MAC address becomes the
root bridge. If you want the device to be the root
bridge, set the root bridge priority to a value
lower than 32768.
(If you enter a number that is
not a multiple of 4096, the switch rounds the
number down.)
Configure Root Guard
The Root Guard feature makes sure that the port on which it is enabled is a designated port. If the Root Guard
enabled port receives a superior BPDU, it goes to a Listening state (for STP) or discarding state (for RSTP and MSTP).
awplus(config)#
interface
<port-list>
Enter Interface Configuration mode for the switch
ports you want to enable Root Guard for.
awplus(config-if)#
spanning-tree guard root
Enable the Guard Root feature for these ports.
awplus(config-if)#
exit
Return to Global Configuration mode.
awplus(config)#
exit
Return to Privileged Exec mode.
Check STP configuration
awplus#
show spanning-tree [interface
<port-list>]
Display the spanning tree configuration for the
device, and confirm the new root bridge priority
(Bridge Priority).
Note that the Bridge ID is in a form like this:
80000000cd240331, and that other IDs follow the
same pattern. This is made up of:
■
8000—the devices’ root bridge priority in
hexadecimal
■
0000cd24033
1
—the devices’ MAC address.
