Using Proxy ARP


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.

 

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