Nortel Networks 2300 Changing Standard Spanning Tree Parameters, Snmp Port Path Cost Defaults

Configuring and Managing Spanning Tree Protocol 313

Changing Standard Spanning Tree Parameters

You can change the following standard STP parameters:

•Bridge priority

•Port cost

•Port priority

Bridge Priority

The bridge priority determines the WSS switch’s eligibility to become the root bridge. You can set this parameter globally or on individual VLANs.

The root bridge is elected based on the bridge priority of each device in the spanning tree. The device with the highest bridge priority is elected to be the root bridge for the spanning tree. The bridge priority is a numeric value from 0 through 65,535. Lower numeric values represent higher priorities. The highest priority is 0, and the lowest priority is 65,535. The default bridge priority for all devices is 32,768.

If more than one device has the highest bridge priority (lowest numeric value), the device with the lowest MAC address becomes the root bridge.

If the root bridge fails, STP elects a new root bridge based on the bridge priorities of the remaining bridges.

Port Cost

Port cost is a numeric value that STP adds to the total cost of a path to the root bridge. When a designated bridge has multiple equal-cost paths to the root bridge, the designated bridge uses the path with the lowest total cost. You can set this parameter on an individual port basis, for all VLANs the port is in, or for specific VLANs.

You can specify a value from 1 through 65,535 for the port cost. The default depends on the port speed and link type. Table 21 lists the defaults for STP port path cost.

Table 21: SNMP Port Path Cost Defaults

Port Speed	Link Type	Default Port Path
		Cost
1000 Mbps	Full Duplex Aggregate Link (Port	19
	Group)
1000 Mbps	Full Duplex	4
100 Mbps	Full Duplex Aggregate Link (Port	19
	Group)
100 Mbps	Full Duplex	18
100 Mbps	Half Duplex	19
10 Mbps	Full Duplex Aggregate Link (Port	19
	Group)

Nortel WLAN Security Switch 2300 Series Configuration Guide