Fundamentals of ND Proxy
When two hosts with the same address prefix communicate with each other, they do not search routing tables. Instead, one of them sends a Neighbor Solicitation (NS) message to obtain the link-layer address corresponding to the destination address, and then uses the link-layer address to encapsulate the data packets to be sent.
In real-world networking scenarios, hosts with the same address prefix may not belong to the same broadcast domain. When this is the case, NS messages cannot be sent to the destination host and therefore the hosts cannot communicate with each other.
To avoid this problem, you can enable ND proxy on the BRAS so that the BRAS replaces the destination host to reply with a Neighbor Advertise (NA) message that carries the link-layer address of the BRAS. In this manner, the two hosts with the same address prefix can communicate with each other through the BRAS.
