In modern service provider and data center networks, customer environments often span both bridged (Layer-2) and routed (Layer-3) domains. This requires seamless interworking between EVPN-based Layer-2 services and Layer-3 VPN routing to ensure consistent connectivity, tenant isolation, and optimal traffic forwarding.
The EVPN IRB (Integrated Routing and Bridging) test validated the correct integration of an EVPN ELAN Layer-2 service with an L3VPN routing service using a symmetric IRB gateway over an SRv6 underlay.
EVPN PE devices learn host MAC and IP information from ARP and Neighbor Discovery messages received from directly connected customer devices. Based on this information, the EVPN PEs create EVPN Type-2 MAC+IP routes, which represent host reachability within the EVPN ELAN. These MAC+IP routes are advertised to remote PEs using BGP EVPN and are transported across the SRv6 core.
In parallel, EVPN access PEs advertise host routes associated with the IRB interface into the L3VPN (IP-VPN) control plane using BGP. All PEs that import the corresponding route targets install these routes in their IP-VRF routing tables, enabling routed reachability between sites.
The IRB gateway was implemented using a BVI bound to the EVPN ELAN and associated with the L3VPN. The gateway IP and MAC addresses are locally significant and are not advertised via either BGP EVPN or BGP VPN.
When traffic destined for a remote subnet is received from an EVPN ELAN host, the Ethernet frame is delivered to the IRB interface using the gateway MAC address. The IRB removes the Layer-2 header and forwards the packet based on an L3VPN route, which is carried across the core using SRv6 encapsulation.
When traffic destined for an EVPN-connected host arrives via the L3VPN, the packet is routed within the IP-VRF to the IRB interface. The IRB performs the Layer-3 to Layer-2 handoff, resolves the destination host MAC using EVPN-learned information, and forwards the frame into the EVPN ELAN.