Proxy advertisement of host MAC+IP type 2 routes in EVPN-VXLAN topology with IRB interfaces

In an Ethernet VPN-Virtual Extensible LAN (EVPN-VXLAN) topology with integrated routing and bridging (IRB) interfaces, leaf devices typically function as Layer 2 gateways. As such, these devices can advertise only the MAC routes (EVPN type 2 routes) for the attached hosts. 

Since the Layer 2 gateways are unable to resolve the MAC-to-IP bindings for the hosts, each of the spine devices, which typically function as Layer 3 gateways, must rely on the Address Resolution Protocol (ARP) and the Neighbor Discovery Protocol (NDP) to discover and install the bindings. 

Devices that function as Layer 3 gateways in this type of topology can advertise the MAC and IP routes (MAC+IP type 2 routes) of hosts. With this feature enabled, after receiving a host MAC route advertisement from a Layer 2 gateway, and ARP and NDP resolve the MAC-to-IP bindings, devices in turn advertises the host MAC and IP routes along with the next hop, which is set to the Layer 2 gateway to which the host is attached. 

Upon receipt of this advertisement, Layer 2 and 3 gateways in the topology install the MAC-to-IP bindings along with the associated next hops. When any of these gateways receives a packet with a destination MAC that matches an address in its MAC table, the gateway can check the next hop associated with the MAC address and forward the packet directly to the Layer 2 gateway to which the host is attached. This resulting packet flow eliminates the need for the packet to be forwarded first to a Layer 3 gateway, which then forwards the packet to the Layer 2 gateway. 

To enable this feature, specify the proxy-macip-advertisement configuration statement at the [edit interfaces irb unit logical-unit-number] hierarchy level. Enabling this feature in an EVPN-VXLAN topology that includes both Layer 2 and Layer 3 gateways is mandatory, while enabling the feature in a topology that includes only Layer 3 gateways is optional.