In the EVPN fabric with Symmetric IRB shown below, the Leaf1 and Leaf2 have been configured as Virtual Terminal End Points (VTEPs) to work with the overlay network. The underlay is built with a 2x2 leaf, spine nodes. Unnumbered BGP is used as the routing protocol for both overlay and underlay networks. The Symmetric IRB model uses a Layer3 VXLAN segment (L3VNI 3000) to route packets between different VNIs.
In the EVPN fabric shown in Figure 3, three VNIs (1002,1006, and 1008) use Symmetric IRB to communicate with each other. The endhosts connected to these VNIs are mapped to three VLANs: 102,106, and 108.
There is also an external router (EXT RTR) that peers with Leaf2 to exchange and advertise an external subnet as a Type-5 route, so the hosts belonging to the EVPN fabric can communicate with the external subnet.
This lab is available on Demo Center (see Support and References for details) as a Hands-on-Lab. Log in to the Demo Center to configure and verify the topology.
Figure 3. Use case deployment