About ND proxy
ND proxy enables a device to answer an NS message requesting the hardware address of a host on another network. With ND proxy, hosts in different broadcast domains can communicate with each other as they would on the same network.
ND proxy includes common ND proxy and local ND proxy.
Common ND proxy
As shown in Figure 59, Interface A with IPv6 address 4:1::99/64 and Interface B with IPv6 address 4:2::99/64 belong to different subnets. Host A and Host B reside on the same network but in different broadcast domains.
Figure 59: Application environment of ND proxy
Because Host A's IPv6 address is on the same subnet as Host B's, Host A directly sends an NS message to obtain Host B's MAC address. However, Host B cannot receive the NS message because they belong to different broadcast domains.
To solve this problem, enable common ND proxy on Interface A and Interface B of the device. The device replies to the NS message from Host A, and forwards packets from other hosts to Host B.
Local ND proxy
As shown in Figure 60, Host A belongs to VLAN 2 and Host B belongs to VLAN 3. Host A and Host B connect to Port B1 and Port B3, respectively.
Figure 60: Application environment of local ND proxy
Because Host A's IPv6 address is on the same subnet as Host B's, Host A directly sends an NS message to obtain Host B's MAC address. However, Host B cannot receive the NS message because they belong to different VLANs.
To solve this problem, enable local ND proxy on Interface A of Device A so that Device A can forward messages between Host A and Host B.
Local ND proxy implements Layer 3 communication for two hosts in the following cases:
The two hosts connect to ports of the same device and the ports must be in different VLANs.
The two hosts connect to isolated Layer 2 ports in the same isolation group of a VLAN.
If super VLAN is used, the two hosts must belong to different sub VLANs.
If Private VLAN is used, the two hosts must belong to different secondary VLANs.