Assistive Address Resolution (AAR) is an optional HLE feature used to avoid sending ARP/ND requests from the home across a WAN to a remote network, or sending ARP/ND requests from the remote network across an access network to a home. The system responds to the ARP/ND request from the network or home with the learned ARP/ND entries, instead of flooding it.
With AAR, the system populates the ARP and neighbor tables with the learned ARP and neighbor entries, using the following methods:
BGP EVPN MAC routes that contain an IP address
(G)ARP/ND/NS packets
When the ISA receives an ARP/ND request, it performs a lookup in the BD’s ARP and neighbor tables by using a target IP address as the key. The following conditions apply:
If the requested IP address is over a different connection, then the ISA generates an ARP/ND reply with the match result without flooding the request.
If the requested IP address is over same connection, then the ISA drops the request. If there is no match, then the ISA floods the address.