Objectives
The simulator ticks each one as soon as the network meets it.
Find the VLT mismatch between L1 and L2 and fix it, so CE bundles both links.
Find why L3 has no tunnel to the L1 and L2 pair, and fix it with automatic route-targets.
Ping PC2 (192.168.10.20) from PC1.
Before you start
show vlt 1 mismatch names anything the peers disagree on. show nve remote-vtep and show evpn evi show a VNI with no tunnels. A manual route-target works, but only if it matches what the others send.
Concept
VLT and MCLAG: two switches, one LACP partner
A leaf pair joined by a peer link looks like one switch to the device below it. That device bundles one link to each leaf with ordinary LACP, so spanning tree blocks nothing and both links forward. Dell OS10 calls this VLT, and SONiC calls it MCLAG. In a VXLAN fabric, the pair also shares one VTEP address, so the rest of the fabric sees a single tunnel endpoint, and either leaf can take the tunnel.
Concept
BGP EVPN: a control plane for VXLAN
BGP EVPN replaces flood-and-learn with BGP routes in the L2VPN EVPN address family. Each VTEP advertises an inclusive-multicast route (type 3) per VNI, so the others know to replicate to it, and a MAC route (type 2) per local host, so remote MACs are known before any traffic flows. A spine is usually the iBGP route reflector.
