Explain EVPN-VXLAN

Question 1

What problem does EVPN-VXLAN solve?

Answer 1

In legacy data centers, traditional VLANs and STP-based L2 networks don’t scale. As east-west traffic grew, we needed a fabric that could scale L2/L3 services across the DC.

Question 2

How would you define EVPN and VXLAN?

Answer 2

• VXLAN is a data-plane encapsulation that allows us to extend L2 domains over L3 infrastructure.
• EVPN is the BGP-based control plane that enables us to advertise MAC and IP reachability between VTEPs.

Question 3

What are the Key Design Elements of EVPN-VXLAN?

Answer 3

• IP or BGP underlay for reachability between VTEPs.
• VTEP (VXLAN Tunnel Endpoint) on the leaf switches.
• VXLAN (data plane) used to encapsulate traffic over the IP underlay.
• EVPN (control plane) uses MP-BGP to advertise MAC/IP (Type-2) and prefix (Type-5) routes.
• Spine switches act as EVPN route reflectors to scale the control plane.
• MLAG to dual hone servers at Leaf switches.
• Direct any cast gateways at Leaf switches.

Question 4

Explain the L3 Gateway Strategy?

Answer 4

We deploy distributed anycast gateways using ip virtual-router address on each leaf, allowing local L3 routing at the edge and removing the need to hairpin traffic through core routers.

Question 5

Summarize the Benefits of EVPN-VXLAN.

Answer 5

• The EVPN-VXLAN design provides Layer 2 scalability.
• Separation of the control and data planes.
• It’s vendor-neutral.
• Supports automation using templates or CVP/Ansible.

Control Plane: BGP EVPN advertises MAC addresses, IPs, and VTEPs proactively.
Data Plane: VXLAN handles actual packet forwarding over the underlay.