Multichassis EtherChannel (MEC) is very similar to cross-stack EtherChannel in principle. The difference is that the feature known as MEC is found on the Catalyst 6500 VSS switches. VSS is a clustering technology that allows multiple 6500 chassis to be configured as a single logical switch. This is similar in principle to a 3750 switch stack. For MEC to be possible, VSS must be properly configured and the switches active in the VSS cluster. See Chapter 17 for more information on VSS configuration.
Once VSS is running, creating MECs is as easy as it is on 3750s. Here, I’ve created a 20 Gb MEC between two 6500s clustered with VSS:
int range ten 1/3/2 , ten 2/3/2VSS(config-if-range)#
channel-group 500 mode on