As the name implies, ECMP means that 2 or more paths with identical properties are available for a switch to forward across to deliver traffic to a particular destination. That said, multiple LAG or MLAG bundles in parallel do qualify as L2 ECMP.īefore we get into the specifics of ECMP, let’s define what ECMP is. Even though there are multiple parallel links that can forward at L2 in an MLAG bundle, they do not function independently of one another. Why? Because any aggregated link bundle presents itself as a single link to the underlying forwarding mechanisms in the switch.

For purposes of this discussion, MLAG does not qualify as L2 ECMP. Another way to achieve forwarding on all links is by leveraging equal cost multipath, or ECMP.ĮCMP comes in both L2 and 元 flavors.

MLAG is one way in which spanning tree limitations are overcome, allowing traffic to safely forward on all links in a multi-chassis bundle, even though the physical topology forms a loop. Switches that have non-blocking forwarding capacity are being wasted if their lit links are not all being utilized. The cabling takes up space in a cabinet or uses costly fiber runs between cabinets. The ports take up real estate in a switch.

Not only is using all link capacity wise from a network design standpoint, but it’s also wise from a financial standpoint.

In data center design, the ability to use all available links to forward traffic is an important consideration. Part 1 of this written series appeared on. This is one of a multi-part series on the Ethernet switching landscape I wrote to support a 2-hour presentation I made at Interop Las Vegas 2014.

L2 tor switch graphics