Configuring the Root Switch

Chapter 6 Configuring STP and RSTP on the ML-Series Card

Configuring STP and RSTP Features

To reenable STP, use the no bridge-groupbridge-group-numberspanning disabled interface-level configuration command.

The switch maintains a separate spanning-tree instance for each active VLAN configured on it. A bridge ID, consisting of the switch priority and the switch MAC address, is associated with each instance. For each VLAN, the switch with the lowest bridge ID becomes the root switch for that VLAN.

Note If your network consists of switches that both do and do not support the extended system ID, it is unlikely that the switch with the extended system ID support will become the root switch. The extended system ID increases the switch priority value every time the bridge ID is greater than the priority of the connected switches that are running older software.

Configuring the Port Priority

If a loop occurs, spanning tree uses the port priority when selecting an interface to put into the forwarding state. You can assign higher priority values (lower numerical values) to interfaces that you want selected first, and lower priority values (higher numerical values) that you want selected last. If all interfaces have the same priority value, spanning tree puts the interface with the lowest interface number in the forwarding state and blocks the other interfaces.

Beginning in privileged EXEC mode, follow these steps to configure the port priority of an interface:

	Command	Purpose
Step 1
Step 1	ML_Series# configure terminal	Enters the global configuration mode.
Step 2
Step 2	ML_Series(config)# interface	Enters the interface configuration mode, and specifies an
	interface-id	interface to configure.
		Valid interfaces include physical interfaces and
		port-channel logical interfaces (port-channel
		port-channel-number).
Step 3
Step 3	ML_Series(config-if)# bridge-group	Configures the port priority for an interface that is an
	bridge-group-number priority-value	access port.
		For the priority-value, the range is 0 to 255; the default is
		128 in increments of 16. The lower the number, the higher
		the priority.
Step 4
Step 4	ML_Series(config-if)# end	Return to privileged EXEC mode.

To return the interface to its default setting, use the no bridge-group id bridge-group-numberpriority-valuecommand.

Cisco ONS 15310-CL and Cisco ONS 15310-MA Ethernet Card Software Feature and Configuration Guide R8.5

	78-18133-01	6-17

15310-CL, 15310-MA specifications

Cisco Systems has established itself as a leader in the networking domain, offering a wide array of solutions to meet the needs of modern businesses. Among its impressive product lineup are the Cisco 15310-CL and 15310-MA routers, designed to provide advanced network performance and reliability.

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Cisco Systems 15310-CL, 15310-MA manual Configuring the Root Switch, Configuring the Port Priority

Models: 15310-CL 15310-MA