20-26
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
OL-4266-08
Chapter 20 Configuring STP and Prestandard IEEE 802.1s MST
Configuring STP
To configure a Cisco 7600 series router as the root bridge, perform this task:
This example shows how to configure the Cisco 7600 series router as the root bridge for VLAN 10, with
a network diameter of 4:
Router#
configure terminal
Router(config)#
spanning-tree vlan 10 root primary diameter 4
Router(config)#
end
Router#
Configuring a Secondary Root Bridge
When you configure a Cisco 7600 series router as the secondary root, the STP bridge priority is modified
from the default value (32768) so that the router is likely to become the root bridge for the specified
VLANs if the primary root bridge fails (assuming the other network devices in the network use the
default bridge priority of 32768).
If the extended system ID is enabled, STP sets the bridge priority to 28672. If the extended system ID is
disabled, STP sets the bridge priority to 16384.
You can run this command on more than one Cisco 7600 series router to configure multiple backup root
bridges. Use the same network diameter and hello time values as you used when configuring the primary
root bridge.
To configure a Cisco 7600 series router as the secondary root bridge, perform this task:
This example shows how to configure the Cisco 7600 series router as the secondary root bridge for
VLAN 10, with a network diameter of 4:
Router#
configure terminal
Router(config)#
spanning-tree vlan 10 root secondary diameter 4
Router(config)#
end
Router#
Command
Purpose
Step 1
Router(config)#
spanning-tree vlan
vlan_ID
root
primary
[
diameter
hops
[
hello-time
seconds
]]
Configures a Cisco 7600 series router as the root bridge.
The
vlan_ID
value can be 1 through 4094, except
reserved VLANs (see
Table 20-5 on page 20-21
).
Router(config)#
no
spanning-tree vlan
vlan_ID
root
Clears the root bridge configuration.
Step 2
Router(config)#
end
Exits configuration mode.
Command
Purpose
Step 1
Router(config)# [
no
]
spanning-tree vlan
vlan_ID
root secondary
[
diameter
hops
[
hello-time
seconds
]]
Configures a Cisco 7600 series router as the secondary
root bridge. The
vlan_ID
value can be 1 through 4094,
except reserved VLANs (see
Table 14-1 on page 14-2
).
Router(config)#
no
spanning-tree vlan
vlan_ID
root
Clears the root bridge configuring.
Step 2
Router(config)#
end
Exits configuration mode.