Question 30 - JN0-683 discussion

Symmetric IRB Routing with EVPN Type 2 Routes:

Symmetric Routing: In symmetric IRB (Integrated Routing and Bridging), routing occurs in both directions at the ingress and egress leaf nodes using the same routing logic. This is contrasted with asymmetric routing, where different routing logic is used depending on the direction of the traffic.

Required Components:

Option A: An L3 IRB interface is necessary for each VLAN that participates in routing, as it handles the Layer 3 processing for the VLAN.

Option B: MAC-VRF is required for symmetric routing to maintain a mapping of MAC addresses to the appropriate VRF, ensuring correct forwarding within the EVPN.

Option D: A transit VNI (Virtual Network Identifier) is required for each VRF to encapsulate the Layer 3 traffic as it traverses the network, allowing the IP traffic to be appropriately forwarded.

Conclusion:

Option A: Correct---Each local VLAN needs an IRB interface for L3 processing.

Option B: Correct---MAC-VRF is necessary for handling MAC address resolution in symmetric routing.

Option D: Correct---Transit VNIs are required for routing VRF-specific traffic across the network.

Options C and E are incorrect because:

C: Symmetric routing can work with various VLAN models, including single or multiple VLANs within an EVPN instance.

E: Symmetric routing is generally more efficient than asymmetric routing as it uses consistent routing logic in both directions.