Switches If the router will be running OSPF, you should add the following commands to the OSPF configuration. (We're not concerned with that here, SO I'm not actually adding it.) router ospf process-id Now we need to configure a switch virtual domain. The domain is a number in the range 1-255: 6509-VE-Left (config) #switch virtual domain ? <1-255> Virtual switch domain number The domain will need to match on both switches. Here I configure the domain to be 100: 6509-VE-Left(config)#switch virtual domain 100 Domain ID 100 config will take effect only after the exec command 'switch convert mode virtual' is issued I will number the switch on the left to be number 1, while the switch on the right will be number 2. Feel free to apply your own preferences as you see fit: 6509-VE-Left(config-vs-domain)#swit 1 You can configure one of the switches to have a higher priority and, using preempt, set one switch to always be preferred. I'm not a fan of this design, however, since failover occurs only by reloading the active switch. Cisco even discourages this in its best prac- tices document (see the end of this chapter for a link). The VSS system does not function like Cisco firewalls, where the active unit can be changed without rebooting. If you'd like to configure preemption, assign a priority to the switch with the switch switch- number priority priority-value command: 6509-VE-Left(config-vs-domain)#switch 1 priority ? <1-255> Virtual switch priority value 6509-VE-Left(config-vs-domain)#switch 1 priority 105 If you want to enable preemption, use the switch switch-number preempt command. Even the switch will tell you that it's a bad idea: 6509-VE-Left (config-vs-domain) #switch 1 preempt ? <15-20> Delay in minutes before standby takes over as active. Default is 15 minutes The default delay is 15 minutes: 6509-VE-Left(config-vs-domain)#switch 1 preempt Please note that Preempt configuration will make the ACTIVE switch with lower priority to reload forcefully when preempt timer expires. The default preempt timer is 15 minut