Alcatel-Lucent OmniSwitch AOS Release 7 - MC-LAG Principle

Configuring Multi-chassis Link Aggregation MC-LAG Overview
OmniSwitch AOS Release 7 Network Configuration Guide March 2011 page 8-11
Example of a MC-LAG Group Network
An important characteristic of this solution relates to the absence of a logical loop between the edge and
multi-chassis peer switches, even though a physical loop does exist.
MC-LAG Principle
In order to ensure a loop free topology, traffic received on one of the ports of an aggregate is never
flooded out to any of the member ports including the receiving port or through the VFL.
In the figure below assume 2 switches connected back to back through an LACP interface. If flooded
traffic (multicast, broadcast, unknown traffic) is received by switch SW2 on Port A, it will not be flooded
out on either Port B or Port C. Additionally, it cannot be sent back out of the same port where it was
received.
Edge
Aggregation
Virtual Fabric
Link
Physical loop
No logical loop to be
guaranteed by the
feature design.
Edge
Aggregation
Virtual Fabric
Link
Physical loop
No logical loop to be
guaranteed by the
feature design.
Edge
Aggregation
MC-LAG-1
Virtual Fabric
Link
Physical loop
No logical loop
guaranteed by the
feature design.