EVPN-VXLAN and Data Center Fabric Integration
EVPN-VXLAN is the fabric model CX 10000 operates within. Candidates should know the roles: VTEPs encapsulate tenant traffic in VXLAN (UDP), while EVPN (BGP address families) distributes MAC/IP reachability and avoids unknown unicast flooding. Understand route types at a high level - Type 2 (MAC/IP), Type 3 (inclusive multicast for BUM), Type 5 (IP prefix) - and how anycast gateways pair with EVPN for distributed L3.
Know the underlay/overlay split: a routed, ECMP underlay carries VXLAN-encapsulated traffic between loopback VTEP addresses; the overlay provides tenant L2/L3 services. Review VNI-to-VLAN mapping, VRF-to-VNI mapping, and MTU requirements (encapsulation adds overhead).
Traps:
- Assuming EVPN eliminates all flooding - BUM still needs Type 3 inclusive multicast (or similar).
- Forgetting MTU headroom on underlay links, causing large-packet drops.
- Mixing up VNI (overlay identifier) with VLAN (local significance).
- Believing the DPU replaces the fabric - services ride on top of EVPN-VXLAN, not instead of it.
Rule of thumb: underlay must be healthy before overlay works. Worked example: hosts on two leaves in the same subnet cannot communicate; check underlay reachability between VTEP loopbacks, confirm the VNI is mapped to the VLAN on both leaves, and verify Type 2 routes exist for both MACs. If Type 2 is missing, the overlay is not advertising - fix BGP EVPN peering first. Verify with show bgp evpn and VXLAN tunnel status.
Also review how distributed services integrate with fabric policy.