Sunday, February 18, 2018

L2 vs. L3 Fabric

I think the general consensus in the last few years has been to choose L3 fabrics, but hoping to see some updated responses in 2018.

L3 fabrics are certainly the way to go for scalability if you have around 1,000 end hosts (or a shitload of access switches). Or another way to think about it, a company that has two ore more Distribution pods from a classic Tier-3 perspective. In these cases, VXLAN + EVPN seem to be taking over, and it would seem mostly due to BUM issues (isolating BUM to a rack or pair of leafs). A secondary reason is that the underlay can use existing silicon, which supports hardware routing of TCP (for BGP) & UDP (for VXLAN).

However, L2 fabrics (i.e. Cisco FabricPath) was great for small shops, where there were only a few hundred end-hosts, or a handful of leaf switches. L3 fabrics and their underlay/overlay solutions seem to be overkill for these small pods, making the solution needlessly complex to manage.

So my question is this: are L2 fabrics dead?

I don't see anything in the news about TRILL, Cisco FP or Brocade VCS anymore (other than it being dead). I hear didly squat from any other vendor. However, the word in the grapevine is that L2 fabrics are still winning the hearts & minds of small shops for 1 simple reason: they truly are plug-n-play.



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