Question 21 - JN0-683 discussion

Symmetric vs. Asymmetric Routing in EVPN-VXLAN:

Symmetric Routing: Traffic enters and exits the VXLAN network through the same VTEP, regardless of the source or destination. This approach simplifies routing decisions, especially in large networks, and is generally more scalable.

Asymmetric Routing: The routing occurs on the egress VTEP. This method can be simpler to deploy in smaller environments but becomes complex as the network scales, particularly with larger numbers of VNIs and VLANs.

Correct Statements:

C . Symmetric routing supports higher scaling numbers: Symmetric routing is preferred in larger EVPN-VXLAN deployments because it centralizes routing decisions, which can be more easily managed and scaled.

D . Asymmetric routing routes traffic on the egress switch: This is accurate, as asymmetric routing means the routing decision is made at the final hop, i.e., the egress VTEP before the traffic reaches its destination.

Incorrect Statements:

A . Symmetric routing needs an extra VLAN with an IRB interface for each L3 VRF instance: This is not accurate. Symmetric routing does not require an extra VLAN per VRF; rather, it uses the same VLAN/VNI across the network, simplifying routing and VLAN management.

B . Asymmetric routing is easier to monitor because of the transit VNI: Asymmetric routing is not necessarily easier to monitor; in fact, it can add complexity due to the split routing logic between ingress and egress points.

Data Center

Reference:

The choice between symmetric and asymmetric routing in an EVPN-VXLAN environment depends on network size, complexity, and specific operational requirements. Symmetric routing is generally more scalable and easier to manage in large-scale deployments.