Mc-Lag Principle - Alcatel-Lucent OmniSwitch AOS Release 7 Manual

Configuring Multi-chassis Link Aggregation
Edge Edge Edge
Physical loop Physical loop Physical loop
No logical loop to be No logical loop to be No logical loop
guaranteed by the guaranteed by the guaranteed by the
feature design. feature design. feature design.
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.
OmniSwitch AOS Release 7 Network Configuration Guide
MC-LAG-1
Example of a MC-LAG Group Network
Aggregation Aggregation Aggregation
March 2011
MC-LAG Overview
Virtual Fabric Virtual Fabric Virtual Fabric
Link Link Link
page 8-11