Configuring A Secondary Root Bridge; Configuring The Rapid Pvst+ Port Priority - Cisco AP775A - Nexus Converged Network Switch 5010 Configuration Manual

Configuring a Secondary Root Bridge

This example shows how to configure the switch as the root bridge for a VLAN:
switch# configure terminal
switch(config)# spanning-tree vlan 5 root primary diameter 4
Configuring a Secondary Root Bridge
When you configure a software switch as the secondary root, the STP bridge priority is modified from the
default value (32768) so that the switch is likely to become the root bridge for the specified VLANs if the
primary root bridge fails (assuming the other switches in the network use the default bridge priority of 32768).
STP sets the bridge priority to 28672.
Enter the diameter keyword to specify the network diameter (that is, the maximum number of bridge hops
between any two end stations in the network). When you specify the network diameter, the software
automatically selects an optimal hello time, forward delay time, and maximum age time for a network of that
diameter, which can significantly reduce the STP convergence time. You can enter the hello-time keyword
to override the automatically calculated hello time.
You configure more than one switch in this manner to have multiple backup root bridges. Enter the same
network diameter and hello time values that you used when configuring the primary root bridge.
With the switch configured as the root bridge, do not manually configure the hello time, forward-delay
Note
time, and maximum-age time using the spanning-tree mst hello-time, spanning-tree mst forward-time,
and spanning-tree mst max-age global configuration commands.
Procedure
Step 1
Step 2
This example shows how to configure the switch as the secondary root bridge for a VLAN:
switch# configure terminal
switch(config)# spanning-tree vlan 5 root secondary diameter 4

Configuring the Rapid PVST+ Port Priority

You can assign lower priority values to LAN ports that you want Rapid PVST+ to select first and higher
priority values to LAN ports that you want Rapid PVST+ to select last. If all LAN ports have the same priority
value, Rapid PVST+ puts the LAN port with the lowest LAN port number in the forwarding state and blocks
other LAN ports.
The software uses the port priority value when the LAN port is configured as an access port and uses VLAN
port priority values when the LAN port is configured as a trunk port.
Cisco Nexus 5000 Series Switch CLI Software Configuration Guide
168
Command or Action
switch# configure terminal
switch(config)# spanning-tree vlan
vlan-range root secondary [diameter
dia [hello-time hello-time]]
Purpose
Enters configuration mode.
Configures a software switch as the secondary root
bridge. The vlan-range value can be 2 through 4094
(except reserved VLAN values.) The dia default is 7.
The hello-time can be from 1 to 10 seconds, and the
default value is 2 seconds.
Configuring Rapid PVST+
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