Short and Sweet Cisco VSS

This post is a short, sweet and to the point copy/paste resource for configuring Cisco’s Virtual Switching System.

Cisco’s Virtual Switching System (VSS) is a pretty common technology that joins two physical Cisco Catalyst switches into one logical switch thereby joining the two data planes. It’s different from stacking switches because you can use regular ethernet cables rather than stackwise cables and modules. The two technologies are otherwise kind of similar in the benefits they offer.

VSS limits you to only two switches in a cluster (switching system), and is used for the 4500, 6500 and 6800 platforms. This is then a great technology to build chassis redundancy at a large distribution or core level. In my mind one of the biggest benefits is multi-chassis etherchannel which provides both link and hardware fault tolerance for your switch uplinks or servers.

Below is an easy copy/paste config you can grab quick rather than dig through a white paper. VSL stands for “virtual switch link” which is the link for VSS traffic between the two switches. This example is from a pair of 4500X switches I put in not long ago and uses 4 port port-channel for the virtual switch link. There will be a bunch of QoS config that gets auto-generated as part of this brief process, and I’d personally tell anyone who asks that you did that part yourself manually and from memory.

Switch 1

conf t switch virtual domain 10 switch 1 exit

int port-channel 5 description VSL for VSS switchport switch virtual link 1 no shut exit

int range ten1/1 – 4 description VSL port for VSS switchport mode trunk channel-group 5 mode on end

switch convert mode virtual

Switch 2

conf t switch virtual domain 10 switch 2 exit

int port-channel 10 description VSL for VSS switchport switch virtual link 2 no shut exit

int range ten1/1 – 4 description VSL port for VSS switchport mode trunk channel-group 10 mode on end

switch convert mode virtual

Verification

sh switch virtual sh switch virtual role sh switch virtual link sh switch virtual link port-channel