Address Resolution Protocol
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Address Resolution Protocol
The Address Resolution Protocol (ARP) is a computer networking protocol for determining a network host's link layer or hardware address when only its Internet Layer (IP) or Network Layer address is known. This function is critical in local area networking as well as for routing internetworking traffic across gateways (routers) based on IP addresses when the next-hop router must be determined. ARP was defined by RFC 826 in 1982.[1] It is Internet Standard STD 37.
ARP has been implemented in many types of networks, such as Internet Protocol (IP) network, CHAOS, DECNET, Xerox PARC Universal Packet, Token Ring, FDDI, IEEE 802.11 and other LAN technologies, as well as the modern high capacity networks, such as Asynchronous Transfer Mode (ATM). Due to the overwhelming prevalence of IPv4 and Ethernet in general networking, ARP is most frequently used to translate IPv4 addresses into Ethernet MAC addresses.
In the next generation Internet Protocol, IPv6, ARP's functionality is provided by the Neighbor Discovery Protocol (NDP).
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Overview and IPv4-plus-Ethernet example
Consider a LAN where machines using IPv4 over Ethernet wish to communicate. A sender wishes to send a message to some other machine on the LAN and knows a destination IPv4 address. The destination IPv4 address is hopefully associated with some appropriate network interface belonging to the recipient machine, and is present on the LAN. But in order for communication to succeed, the sending machine first needs to discover the ethernet MAC address of the intended recipient network interface. This requirement comes about because Ethernet hardware does not (necessarily) understand IPv4 protocols or IPv4 addresses in the sense that Ethernet hardware 'listens out for' relevant Ethernet MAC addresses but does not 'listen out for' IPv4 addresses. (An impractical alternative would be
Address Resolution Protocol
The Address Resolution Protocol (ARP) is a computer networking protocol for determining a network host's link layer or hardware address when only its Internet Layer (IP) or Network Layer address is known. This function is critical in local area networking as well as for routing internetworking traffic across gateways (routers) based on IP addresses when the next-hop router must be determined. ARP was defined by RFC 826 in 1982.[1] It is Internet Standard STD 37.
ARP has been implemented in many types of networks, such as Internet Protocol (IP) network, CHAOS, DECNET, Xerox PARC Universal Packet, Token Ring, FDDI, IEEE 802.11 and other LAN technologies, as well as the modern high capacity networks, such as Asynchronous Transfer Mode (ATM). Due to the overwhelming prevalence of IPv4 and Ethernet in general networking, ARP is most frequently used to translate IPv4 addresses into Ethernet MAC addresses.
In the next generation Internet Protocol, IPv6, ARP's functionality is provided by the Neighbor Discovery Protocol (NDP).
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Overview and IPv4-plus-Ethernet example
Consider a LAN where machines using IPv4 over Ethernet wish to communicate. A sender wishes to send a message to some other machine on the LAN and knows a destination IPv4 address. The destination IPv4 address is hopefully associated with some appropriate network interface belonging to the recipient machine, and is present on the LAN. But in order for communication to succeed, the sending machine first needs to discover the ethernet MAC address of the intended recipient network interface. This requirement comes about because Ethernet hardware does not (necessarily) understand IPv4 protocols or IPv4 addresses in the sense that Ethernet hardware 'listens out for' relevant Ethernet MAC addresses but does not 'listen out for' IPv4 addresses. (An impractical alternative would be