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Configuring a Root Switch
learning before reaching the forwarding state. For information about PortFast, see the
"Understanding How PortFast Works" section on page 9-2
PortFast, UplinkFast, BackboneFast, and Loop Guard."
To configure the spanning tree parameters to improve convergence, perform this task in privileged
mode:
Task
Step 1
Configure the hello time for a VLAN or an
MISTP instance.
Step 2
Verify the configuration.
Step 3
Configure the forward delay time for a
VLAN or an MISTP instance.
Step 4
Verify the configuration.
Step 5
Configure the maximum aging time for a
VLAN or an MISTP instance.
Step 6
Verify the configuration.
This example shows how to configure the spanning tree Hello Time, Forward Delay Timer, and
Maximum Age Timer to 2, 4, and 4 seconds respectively:
Console> (enable) set spantree hello 2 100
Spantree 100 hello time set to 7 seconds.
Console> (enable)
Console> (enable) set spantree fwddelay 4 100
Spantree 100 forward delay set to 21 seconds.
Console> (enable)
Console> (enable) set spantree maxage 6 100
Spantree 100 max aging time set to 36 seconds.
Console> (enable)
Console> (enable) set spantree root 1-10 dia 4
VLANs 1-10 bridge priority set to 8192
VLANs 1-10 bridge max aging time set to 14 seconds.
VLANs 1-10 bridge hello time set to 2 seconds.
VLANs 1-10 bridge forward delay set to 9 seconds.
Switch is now the root switch for active VLANs 1-6.
Console> (enable)
Using Root Guard—Preventing Switches from Becoming Root
You may want to prevent switches from becoming the root switch. The root guard feature forces a port
to become a designated port so that no switch on the other end of the link can become a root switch.
When you enable root guard on a per-port basis, it is automatically applied to all of the active VLANs to
which that port belongs. When you disable root guard, it is disabled for the specified port(s). If a port goes
into the root-inconsistent state, it automatically goes into the listening state.
Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4
8-34
Chapter 8
in
Chapter 9, "Configuring Spanning Tree
Command
set spantree hello interval [vlan] mistp-instance
[instances]
show spantree [vlan | mistp-instance instances]
set spantree fwddelay delay [vlan] mistp-instance
[instances]
show spantree [mod/port] mistp-instance [instances]
[active]
set spantree maxage agingtime [vlans] mistp-instance
instances
show spantree [mod/port] mistp-instance [instances]
[active]
Configuring Spanning Tree
78-13315-02
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