Administrator Guide

Link Aggregation 1055
Multi-Switch LAG (MLAG)
Overview
In a typical layer-2 network, the Spanning Tree Protocol (STP) is deployed to
avoid packet storms due to loops in the network. To perform this function,
STP sets ports into either a forwarding state or a blocking state. Ports in the
blocking state do not carry traffic. In the case of a topology change, STP re-
converges to a new loop-free network and updates the port states. STP is
relatively successful mitigating packet storms in the network, but redundant
links in the network are blocked from carrying traffic by the spanning tree
protocol.
In some network deployments, redundant links between two switches are
bundled together in a Link Aggregation Group (LAG) and appear as a single
link in the spanning tree topology. The advantage is that all LAG member
links can be in the forwarding state and a link failure can be recovered in
milliseconds. This allows the bandwidth on the redundant links to be utilized.
However, LAGs are limited to connecting multiple links between two partner
switches, which leaves the switch as a single point of failure in the topology.
Dell EMC Networking MLAG extends the LAG bandwidth advantage across
multiple Dell EMC Networking N-Series switches connected to a LAG
partner device. The LAG partner device is unaware that it is connected over a
LAG to two peer Dell EMC Networking N-Series switches; instead, the two
switches appear as a single switch with a single MAC address to the partner.
All links can carry data traffic across a physically diverse topology and in the
case of a link or switch failure, traffic can continue to flow with minimal
disruption.
NOTE: This feature is not available on the Dell EMC Networking N1100-ON or
N1500 Series switches.