ARP is done actually to get the MAC-address of the host from the IP address.
When a host sends a ARP request for a machine in the same subnet, it gets a response from the destination host directly.
When the host is not on the same subnet, the device actually sends the packet to the default gateway.
Routers can be configured to send the proxy arp, a technique for using the ARP protocol to provide an ad hoc routing mechanism.
A multi-port networking device (e.g. a router) implementing Proxy ARP will respond to ARP requests on one interface as being responsible for addresses of device addresses on another interface. The device can then receive and forward packets addressed to the other devices
http://www.erg.abdn.ac.uk/users/gorry/course/inet-pages/arp.html
HTH, rate if it does
Narayan
