Explains when the router answers ARP requests on behalf of another device and how to enable proxy ARP or local proxy ARP for different network relationships.
Proxy ARP functions are address-resolution functions that
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let the router answer eligible ARP requests with its own local data-link address
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help hosts reach destinations without requiring the hosts to understand routing, and
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support either destinations on other physical networks or destinations on the same Layer 3 network, depending on the configured function.
Proxy ARP behavior
When proxy ARP is disabled, the router responds only when the target is the receiving interface address or has a statically configured ARP alias.
When proxy ARP is enabled, the router also responds when the target is on another physical network, the router has a route to the target, and every route to the target uses an interface other than the receiving interface.
Local proxy ARP behavior
Local proxy ARP applies when the target, source, and receiving interface addresses are on the same Layer 3 network and the next hop to the target uses the receiving interface.
Local proxy ARP commonly resolves addresses for devices on the same Layer 3 network that are separated at Layer 2, such as devices in private VLANs. It supports the interface types supported by ARP, including unnumbered interfaces.