16- and 36-Port Ethernet Switch Module for Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series
Configuration Tasks
125
Cisco IOS Release 12.2(2)XT, 12.2(8)T, and 12.2(15)ZJ
Note
Only network administrators with a good understanding of how switches and STP function should
make adjustments to spanning-tree parameters. Poorly planned adjustments can have a negative
impact on performance. A good source on switching is the IEEE 802.1d specification; for more
information, refer to the “References and Recommended Reading” appendix in the Cisco IOS
Configuration Fundamentals Command Reference, Release 12.2.
Changing the Switch Priority
You can globally configure the priority of an individual switch when two switches tie for position as the
root switch, or you can configure the likelihood that a switch will be selected as the root switch. This
priority is determined by default; however, you can change it.
Beginning in privileged EXEC mode, follow these steps to change the switch priority:
No no form of this command exists. To return to the default setting, use the bridge bridge-group priority
number global configuration command, and set the priority to the default value. To change the priority
on an interface, use the bridge-group priority interface configuration command (described in the next
section).
Changing the Interface Priority
You can change the priority for an interface. When two switches tie for position as the root switch, you
configure an interface priority to break the tie. The switch with the lowest interface value is elected.
Beginning in privileged EXEC mode, follow these steps to change the interface priority:
Command
Purpose
Step 1
configure terminal
Enters global configuration mode.
Step 2
bridge bridge-group priority number
Changes the priority of the switch.
•
For bridge-group, specify the bridge group number. The range is 1
to 255.
•
For number, enter a number from 0 to 65535. The default is 32768.
The lower the number, the more likely the switch will be chosen as
the root.
Step 3
end
Returns to privileged EXEC mode.
Step 4
show running-config
Verifies your entry.
Step 5
copy running-config startup-config
(Optional) Saves your entry in the configuration file.
Command
Purpose
Step 1
configure terminal
Enters global configuration mode.
Step 2
interface interface-id
Enters interface configuration mode, and specifies the interface to set
the priority.