Virtual Switch System

The fundamental reason for employing a VSS is to logically combine a pair of switches into a single network element.

The VSS active and standby switches perform packet forwarding for ingress data traffic on their locally hosted interfaces. However, the VSS standby switch sends all control traffic to the VSS active switch for processing.

The virtual switch link (VSL) is a special link that carries control and data traffic between the two switches of a VSS.

Data traffic is load balanced  among the VSL links by either the default or the configured EtherChannel load-balancing algorithm.

MultiChasis EtherChannel (MCE)

Layer 2 protocols operate on the EtherChannel as a single logical entity.

VSS enables the creation of Multichassis EtherChannel (MEC), which is an EtherChannel whose member ports can be distributed across the member switches in a VSS.

A VSS can support a maximum of 256 EtherChannels.

VSS Configuration

You have to create the same virtual switch domain on both sides of the VSS.

Switch domain number must fall between 1 and 255.
During the configuration, both port channels are set up on the VSS active switch.
Check that both port channel numbers are available on both of the peer switches.

 SW1#switch virtual domain 10
 SW1#switch 1
 SW1#exit

 SW2#switch virtual domain 10
 SW2#switch 2
 SW2#exit

 SW1#int port-channel 5
 SW1#switchport
 SW1#switch virtual link 1
 SW1#no shut
 SW1#exit

 SW2#int port-channel 10
 SW2#switchport
 SW2#switch virtual link 2
 SW2#no shut
 SW2#exit

 SW1#int range g7/3 - 4
 SW1#switchport mode trunk
 SW1#channel-group 5 mode on
 SW1#exit

 SW2#int range g4/4 - 5
 SW2#switchport mode trunk
 SW2#channel group 10 mode on
 SW2#exit

 SW1#switch convert mode virtual
 reboot

 SW2#switch convert mode virtual
 reboot

Verification
 #show switch virtual
 #show switch virtual role
 #show switch virtual link
 #show switch virtual link port-channel