es. It is set to the approximate time required to bring up all linecards in a fully loaded chassis. Once the preempt timer starts, the standby switch with higher priority will take over as active after 15 minutes. Installing VSS If you change your mind, just negate the command. There is no fanfare when you do this: 6509-VE-Left(config-vs-domain #no switch 1 preempt When using VSS, you can manually set the MAC addresses to be used by the virtual switch, but the easier way to go in most installations is to let the switch assign virtual MACs from a predetermined range. Do this with the mac-address use-virtual command: 6509-VE-Left (config-vs-domain) #mac-address ? H.H.H Manually set router mac address use-virtual Use mac-address range reserved for Virtual Switch System 6509-VE-Left(config-vs-domain) #mac-address use-virtual The link that connects the two switches together and acts like a stacking cable is called the virtual switch link (VSL). This link should have as many high-speed links as you can spare, and they should be distributed across multiple modules. They should also be installed in powers of two for optimal hashing. You don't want this link to fail, SO make it as resilient as possible. For our design, we've got four 10 Gb Ethernet links making up the VSL. The VSL EtherChannel must be different on each switch SO that when the two switches merge, they will be able to differentiate which side of the link belongs to which physical switch. This is the only time you'll need to have a different configuration for a single port channel with VSS. Watch out for this, since it seems to be counterintuitive to everyone I've taught. I've configured Po10 on the left and Po20 on the right. These port channels must be assigned as the SVL using the switch virtual link core-switch-number command. The core-switch-number is the switch number we configured in the switch virtual domain section: 6509-VE-Left(config)#int port-channel 10 6509-VE-Left(config-if)#switch virtual link 1 Let's add some physical ports to the port channe