About enabling proxy ARP

Proxy ARP allows a routing switch to answer ARP requests from devices on one network on behalf of devices in another network. Since ARP requests are MAC-layer broadcasts, they reach only the devices that are directly connected to the sender of the ARP request. Thus, ARP requests do not cross routers.

For example, if Proxy ARP is enabled on a routing switch connected to two subnets, and, the routing switch can respond to an ARP request from for the MAC address of the device with IP address In standard ARP, a request from a device in the subnet cannot reach a device in the subnet if the subnets are on different network cables, and thus is not answered.

An ARP request from one subnet can reach another subnet when both subnets are on the same physical segment (Ethernet cable), since MAC-layer broadcasts reach all the devices on the segment.