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Chapter 16
Configuring STP
The root switch for each spanning-tree instance should be a backbone or distribution switch. Do not
Note
configure an access switch as the spanning-tree primary root.
Use the diameter keyword to specify the Layer 2 network diameter (that is, the maximum number of
switch hops between any two end stations in the Layer 2 network). When you specify the network
diameter, the switch automatically sets an optimal hello time, forward-delay time, and maximum-age
time for a network of that diameter, which can significantly reduce the convergence time. You can use
the hello keyword to override the automatically calculated hello time.
After configuring the switch as the root switch, we recommend that you avoid manually configuring the
Note
hello time, forward-delay time, and maximum-age time through the spanning-tree vlan vlan-id
hello-time, spanning-tree vlan vlan-id forward-time, and the spanning-tree vlan vlan-id max-age
global configuration commands.
Beginning in privileged EXEC mode, follow these steps to configure a switch to become the root for the
specified VLAN. This procedure is optional.
Command
Step 1
configure terminal
Step 2
spanning-tree vlan vlan-id root primary
[diameter net-diameter [hello-time seconds]]
Step 3
end
Step 4
show spanning-tree detail
Step 5
copy running-config startup-config
To return to the default setting, use the no spanning-tree vlan vlan-id root global configuration
command.
OL-8915-03
Purpose
Enter global configuration mode.
Configure a switch to become the root for the specified VLAN.
For vlan-id, you can specify a single VLAN identified by
•
VLAN ID number, a range of VLANs separated by a
hyphen, or a series of VLANs separated by a comma. The
range is 1 to 4094.
(Optional) For diameter net-diameter, specify the
•
maximum number of switches between any two end
stations. The range is 2 to 7.
(Optional) For hello-time seconds, specify the interval in
•
seconds between the generation of configuration messages
by the root switch. The range is 1 to 10; the default is 2.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
Configuring Spanning-Tree Features
16-15
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Troubleshooting
