Ian Nightingale published an interesting story of connectivity problems he had in a VXLAN-based campus network. TL&DR: it’s always the MTU (unless it’s DNS or BGP).

The really fun part: even though large L2 segments might have magical properties (according to vendor fluff), there’s no host-to-network communication in transparent bridging, so there’s absolutely no way that the ingress VTEP could tell the host that the packet is too big. In a layer-3 network you have at least a fighting chance…

For more details, watch the Switching, Routing and Bridging part of How Networks Really Work webinar (most of it available with Free Subscription).