Blog Posts in October 2025

In the EVPN Designs: Layer-3 Inter-AS Option A, I described the simplest multi-site design in which the WAN edge routers exchange IP routes in individual VRFs, resulting in two isolated layer-2 fabrics connected with a layer-3 link.

Today, let’s explore a design that will excite the True Believers in end-to-end layer-2 networks: two EVPN fabrics connected with an EBGP session to form a unified, larger EVPN fabric. We’ll use the same “physical” topology as the previous example; the only modification is that the WA-WB link is now part of the underlay IP network.