Category: Link Aggregation

In the Multi-chassis Link Aggregation (MLAG) Basics post I’ve described how you can use (usually vendor-proprietary) technologies to bundle links connected to two upstream switches into a single logical channel, bypassing the Spanning Tree Protocol (STP) port blocking. While every vendor takes a different approach to MLAG, there are only a few architectures that you’ll see. Let’s start with the most obvious one: stacking on steroids.

If you ask any networking engineer building layer-2 fabrics the traditional way about his worst pains, I’m positive Spanning Tree Protocol (STP) will be very high on the shortlist. In a well-designed fully redundant hierarchical bridged network where every device connects to at least two devices higher in the hierarchy, you lose half the bandwidth to STP loop prevention whims.