Active-active layer 2

VSX LAGs span two switches and operate in active-active mode. Traffic between the access layer and aggregation layer switches can be forwarded to any of the active links. There are no loops and no need for spanning tree protocol or blocked ports.

From a datapath perspective, each VSX switch that gets a packet always uses its local links of the LAG to forward traffic to the destination. The VSX switch only uses the ISL link if the local LAG links are down.

The following shows the configuration details from the figure:

interface lag 11 multi-chassis
	description access-sw1
	no shutdown
	no routing
	vlan trunk native 1
	vlan trunk allowed 5,10,15,20
	lacp mode active

interface lag 12 multi-chassis
	description access-sw2
	no shutdown
	no routing
	vlan trunk native 1
	vlan trunk allowed 5,10,15,20
	lacp mode active

interface 1/1/1
	no shutdown
	lag 11
interface 1/1/2
	no shutdown
	lag 12