H3C Technologies H3C SecPath F1000-E - Manual (Page 281)

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Configuring proxy ARP
The proxy ARP configuration is available only at the CLI.
Overview
Proxy ARP includes common proxy ARP and local proxy ARP.
• Common proxy ARP allows communication when a sending host considers the receiving host to be
on the same subnet, but the receiving host actually resides on a different subnet.
• Local proxy ARP allows communication between hosts that reside on the same subnet but are
isolated at Layer 2.
In both cases, a device located between the two hosts must respond to the request with the MAC address
of the receiving interface to allow Layer 3 communication between the two hosts. This is achieved by
proxy ARP, which hides the physical details of the network.
Common proxy ARP
A common proxy ARP enabled device allows hosts that reside on different subnets to communicate.
As shown in
Figure 163 , Router connects to two subnets through Ethernet 1/1 and Ethernet 1/2. The IP
addresses of the two interfaces are 192.168.10.99/24 and 192.168.20.99/24. Host A and Host B are
assigned the same prefix 192.168.0.0 assigned . Host A connects to Ethernet 1/1 and Host B connects
to Ethernet 1/2.
Figure 163 Application environment of common proxy ARP
Because Host A considers that Host B is on the same network, it broadcasts an ARP request for the MAC
address of Host B. However, Host B cannot receive this request because it is in a different broadcast
domain.
You can enable common proxy ARP on Ethernet 1/1 of Router so that Router can reply to the ARP request
from Host A with the MAC address of Ethernet 1/1, and forward packets sent from Host A to Host B. In
this case, Router acts as a proxy of Host B.
A main advantage of common proxy ARP is that you can enable it on a single router without disturbing
routing tables of other routers in the network. Proxy ARP acts as the gateway for hosts that are not
configured with a default gateway or do not have routing capability.