BGP

EVPN multihoming vs MLAG: what actually breaks Both make two leaf switches look like one LACP partner to a dual-homed server. Both forward on both links. So which one holds up when something fails? Two labs on Cumulus Linux, identical wiring, four failure scenarios, every probe accounted for.

Type-2 gets all the attention, but a datacenter fabric runs on five core EVPN route types and quietly depends on every one. Here is what each actually carries, decoded from a live multihomed fabric, including the two types MLAG labs never get to show you.

Anycast usually lets the network decide which datacenter answers. I moved that decision onto two GoBGP hosts that watch both datacenters and steer a single global VIP between them. Here's the design, the traffic flow, and three failover drills that came through with zero failed requests.

Two elephant flows, six trials, six collisions: one uplink carried everything while its twin sat at zero, and every dashboard stayed green. The measured polarization, the four-witness diagnostic chase, and the birthday math production fabrics live with.

The finale: one request traced live through all eight hops the series built, the five traps ranked by hours lost, and what I would do differently next time. Plus the honest single point of failure the design still carries.

Wiring Active/Active firewalls into the fabric: four eBGP sessions, thirteen prefixes up and one default down, device-bound NAT, two DNAT pinholes for all inbound traffic, and the vPC SVI timer lesson.

VXLAN tunnels between loopbacks, EVPN as the directory, anycast gateways everywhere, and the route-target auto trap that silently empties eBGP fabrics. With the complete overlay configs for all twelve switches.

Twelve switches become a fabric: loopbacks, /31s, jumbo MTU, and eBGP as the only routing protocol. Plus the promised look inside a vPC leaf pair, and the three-command verification that proves the underlay.

How my bare-metal k8s cluster gets cloud-style LoadBalancer IPs: Cilium allocates a VIP, every node advertises it over eBGP to the NX-OS leaves, and the fabric ECMPs traffic into the cluster. Full walk from IPAM pool to leaf routing table.