This description was taken from the Software Reference Guide, see
at www.bintec.de
ARP (Address Resolution Protocol) is a technique used to map an IP ad-dresses
to a physical network address, or MAC address. Normally, ARP re-quests
for the hardware address of a particular IP address are answered by
the station the IP address is assigned to. With proxy ARP, the request can be
alternatively answered by the BRICK. This is useful when a host on your
network is connected via an ISDN line.
Each interface in the ipExtIfTable can be configured for proxy ARP by
setting its respective ipExtIfProxyArp variable to "on".
When proxy ARP is switched on for this interface, all ARP requests for
the target host are answered by the BRICK. IP datagrams destined for this
host are sent directly to the BRICK and are forwarded to the real host. The
benefit of proxy ARP is that no routing entries need to be made for such
hosts.
Once proxy ARP is enabled, the BRICK interprets all ARP requests it re-ceives.
The IP address for which the hardware address is requested, is
passed through the ipRouteTable. If the BRICK detects that it must route the
request to a different interface from which the request was received on, it
answers the request with its own hardware address, i.e, all further packets
for this IP address to be sent to the BRICK.
NOTE: Proxy ARP may cause problems on systems that check for security
viola tions where two IP addresses map to the same physical adress.