DELL N3000 User Manual

Configuring Link Aggregation

In a typical L2 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 Networking MLAG extends the LAG bandwidth advantage across 

multiple Dell Networking switches connected to a LAG partner device. The 

LAG partner device is oblivious to the fact that it is connected over a LAG to 

two peer Dell Networking switches - instead, the two switches appear as a 

single switch 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.