The Virtual Switching System (VSS) allows two Cisco
Catalyst 6500 or 4500 chassis to bond together so that is seen as a
single virtual swich to the rest of the network. Other devices will see
the VSS configured 6500 as a single device which means it’s possible to
use multi chassis etherchannel and protocols like spanning-tree will
only see a single switch.
Some other features are NSF (Non Stop Forwarding) / SSO (Stateful
Switchover) which means that when a single chassis fails the other one
will take over without any downtime since the routing table / CEF table
etc. are stored in both chassis’ supervisors.
Another cool feature is EFSU (Enhanced Fast Software Upgrade) which allows you to upgrade the IOS version without any downtime.
In this tutorial I will be using two Cisco Catalyst 6504 switches
with 720-10G VSS supervisors to show you how to configure VSS and verify
that it’s working.