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An Address Resolution Protocol cache (ARP cache) is a repository for data that is used to connect an IP address to a Media Access Control (MAC) address for a physical machine or device in a local network. The ARP cache can hold data for both wireless and Ethernet routing, and helps to route packets to the right endpoint.
One main role of an ARP cache is to accommodate ARP requests where a gateway has to deal with where to send packets within a local network. For consumers, the gateway is often part of the Internet Service Provider infrastructure. The gateway may generate an ARP request, where the system will use information in the ARP cache to find the right connected device for a given address.
Some issues with an ARP cache relate to "resolving" an IP address to a MAC address. To this end, dynamic ARP cache setups have been created, where a registered address will be kept for reference for a specific length of time. This helps to limit problems with ARP address resolution.