Dell OS10: a VLT pair (Dell OS10 lab)

Objectives

The simulator ticks each one as soon as the network meets it.

On L1 and L2, create VLAN 10.
Build vlt-domain 1: discovery-interface ethernet1/1/5-1/1/6, the same vlt-mac on both, primary-priority 1 on L1 and 8192 on L2, peer-routing, and the other switch as backup destination (172.16.0.2 from L1, 172.16.0.1 from L2).
On both, build port-channel 1 in VLAN 10 with vlt-port-channel 1, and add ethernet1/1/3 with LACP.
CE bundles both its links: show vlt 1 vlt-port-detail shows port-channel 1 up.
On L2, put ethernet1/1/7 in VLAN 10, then ping PC2 from PC1.

Before you start

Discovery interfaces build the VLT interconnect automatically as port-channel 1000. The backup destination only tells a peer whether its partner is alive when that interconnect fails, so the pair forms without it. show vlt 1 mismatch lists anything that differs.

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.