Proxy ARP

Proxy ARP is a technique by which a device on a given network answers the queries for an IP address that is not on that network. The ARP Proxy is aware of the location of the traffic's destination, and offers its own MAC address as (ostensibly final) destination. The "captured" traffic is then typically routed by the Proxy to the intended destination via another interface or via a .

The process which results in the node responding with its own MAC address to an ARP request for a different IP address for proxying purposes is sometimes referred to as 'publishing'.

Below are some typical uses for proxy ARP:

Disadvantage of Proxy ARP include scalability (ARP resolution is required for every device routed in this manner) and reliability (no fallback mechanism is present, and masquerading can be confusing in some environments). ARP manipulation techniques, however, are the basis for protocols providing redundancy on broadcast networks (e.g., Ethernet), most notably and .

Proxy ARP can create DoS attacks on networks if misconfigured. For example, a misconfigured router with proxy ARP has the ability to receive packets destined for other hosts (as it gives its own MAC address in response to ARP requests for other hosts/routers), but may not have the ability to correctly forward these packets on to their final destination, thus blackholing the traffic.

Proxy ARP can "hide" device misconfigurations, such as a missing or incorrect default gateway.

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