Users Guide

878 Spanning Tree Protocol
RSTP-PV Aggregation-Layer Switch Configuration Example
In this configuration example, two aggregation-layer switches are configured.
Ports 1–4 are configured in a LAG connecting the two aggregation-layer
switches. Ports 12–24 are configured as down-links to twelve access-layer
switches configured as in the previous example. Down-links to the access-
layer switches have physical diversity; there is one downlink to each of the
twelve access-layer switches from each of the paired aggregation-layer
switches.
The uplink ports to the network core are configured as LAGs to provide link
redundancy. It is presumed that the core links connect to a router running
RSTP-PV. The configuration for the two aggregation-layer switches is
identical, except for the diversity configuration noted below.
For forwarding diversity, the even numbered switch is made the root for the
even-numbered VLANs. The odd numbered switch is made the root for the
odd-numbered VLANs.
1 Create VLANs 2 through 4:
console#configure
console(config)#vlan 2-4
console(config-vlan2-4)#exit
2 Enable RSTP-PV:
console(config)#spanning-tree mode rapid-pvst
3 Configure for a max network diameter of 4:
console(config)#spanning-tree vlan 1-4 max-age 16
4 Configure one downlink trunk port per downlink switch:
console(config)#interface range te1/0/12-24
console(config-if-Te1/0/12-24)#switchport mode trunk
exit
5 Configure forwarding diversity for the even numbered switches:
console(config)#spanning-tree vlan 2,4 root primary
console(config)#spanning-tree vlan 1,3 root secondary
6 Configure forwarding diversity for the odd numbered switches:
console(config)#spanning-tree vlan 1,3 root primary
console(config)#spanning-tree vlan 2,4 root secondary
7 Configure two uplink ports per uplink switch:
console(config)#interface range fo1/0/1-2