Understanding Asymmetric and Symmetric IRB in EVPN-VXLAN Fabrics
EVPN-VXLAN becomes easier to understand when viewed as packet flow, with IRB enabling leaf switches to bridge within subnets and route between subnets, and the fabric’s design hinging on two primary IRB approaches.
MAIN POINTS
- EVPN-VXLAN complexity is clearer when tracing packets instead of studying protocols separately.
- IRB lets a leaf switch perform both Layer 2 bridging and Layer 3 routing.
- Bridging handles traffic within a subnet, while routing moves traffic between subnets.
- The fabric uses two main IRB models to support these functions.
TAKEAWAYS
- Packet-level thinking is a practical way to understand EVPN-VXLAN behavior.
- IRB is the key mechanism that combines switching and routing at the leaf.
- Subnet-local traffic and inter-subnet traffic are handled differently in the fabric.
- The architecture centers on choosing between two IRB designs.