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Chapter 41: Spanning Tree Protocol (STP) Procedures
584
Setting the Switch Parameters
This table lists the STP functions that are controlled at the switch level.
These commands are located in the Global Configuration mode and apply
to the entire switch.
Unless you are familiar with their functions, you should not change the
forward time, hello time, and max-age parameters from their default
values on the switch. These parameters have to be set in accordance with
the following formulas, as specified in IEEE Standard 802.1d:
max-age <= 2 x (forward time - 1.0 second)
max-age => 2 x (hello time + 1.0 second)
This example changes the forward time to 24 seconds, the hello time to 5
seconds and the max-age to 20:
awplus> enable
awplus# configure terminal
awplus(config)# spanning-tree forward-time 24
awplus(config)# spanning-tree hello-time 5
awplus(config)# spanning-tree max-age 20
If you want the switch to be the root bridge of the spanning tree domain,
assign it a low priority number with the SPANNING-TREE PRIORITY
command. The bridge priority has a range 0 to 61,440 in increments of
4.096. The default value is 32,768.
Table 60. STP Switch Parameter Commands
To Use This Command Range
Specify how long the ports remain in
the listening and learning states
before entering the forwarding state.
SPANNING-TREE FORWARD-TIME
forwardtime
4 to 30
seconds
Configure how frequently the switch
sends spanning tree configuration
information when it is functioning as
the root bridge or trying to become the
root bridge.
SPANNING-TREE HELLO-TIME
hellotime
1 to 10 seconds
Configure how long the switch stores
bridge protocol data units (BPDUs)
before deleting them.
SPANNING-TREE MAX-AGE maxage 6 to 40 seconds
Assign the switch a priority number,
which is used to determine the root
bridge in the spanning tree domain.
SPANNING-TREE PRIORITY priority 0 to 61,440, in
increments of
4,096