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What is ARP?
ARP, which stands for Address Resolution Protocol in English, is the most widely used network interface in the creation of local networks. Systems can easily be added to LANs by attaching network cards that serve as Ethernet interfaces. Ethernet interfaces use the physical addresses given to them during production to send data packets to each other; these interfaces are 48 bits long, with the first 24 bits identifying the manufacturer and the 48-bit block being unique. In networks using the TCP/IP protocol, a 32-bit IP address is used. When an Ethernet interface is used at the physical layer, it is necessary to perform address resolution from IP address to physical address. For this purpose, systems use ARP (Address Resolution Protocol), a protocol for address resolution.
ARP Packet Formats:
An ARP message structure has been created to facilitate messaging in necessary situations. While this message structure aims at physical/hardware address resolution for any protocol, it is generally used to obtain an Ethernet address in IP networks.
Hardware Address Type
A number given to each data link layer protocol for use in this field. For example, Ethernet 1.
Protocol Address Type
A number given for each protocol to use in this field. For example, IP 0x0800.
Hardware Address Length
Indicates the length of the hardware address in bytes. An Ethernet address is 6 bytes long.
Protocol Address Length
Logical address length in bytes. An IPv4 address is 4 bytes long.
Operation
Specifies the sender's operation: 1 for request, 2 for reply, 3 for RARP request, and 4 for RARP reply.
Sender Hardware Address
Sender's hardware address.
Sender Protocol Address
Sender's protocol address.
Target Hardware Address
Hardware address for the recipient. Requests disregard this field. When sending a request message, the entire Target Hardware Address is set to zero.
Target Protocol Address
Protocol address for the recipient.
ARP, which stands for Address Resolution Protocol in English, is the most widely used network interface in the creation of local networks. Systems can easily be added to LANs by attaching network cards that serve as Ethernet interfaces. Ethernet interfaces use the physical addresses given to them during production to send data packets to each other; these interfaces are 48 bits long, with the first 24 bits identifying the manufacturer and the 48-bit block being unique. In networks using the TCP/IP protocol, a 32-bit IP address is used. When an Ethernet interface is used at the physical layer, it is necessary to perform address resolution from IP address to physical address. For this purpose, systems use ARP (Address Resolution Protocol), a protocol for address resolution.
ARP Packet Formats:
An ARP message structure has been created to facilitate messaging in necessary situations. While this message structure aims at physical/hardware address resolution for any protocol, it is generally used to obtain an Ethernet address in IP networks.
Hardware Address Type
A number given to each data link layer protocol for use in this field. For example, Ethernet 1.
Protocol Address Type
A number given for each protocol to use in this field. For example, IP 0x0800.
Hardware Address Length
Indicates the length of the hardware address in bytes. An Ethernet address is 6 bytes long.
Protocol Address Length
Logical address length in bytes. An IPv4 address is 4 bytes long.
Operation
Specifies the sender's operation: 1 for request, 2 for reply, 3 for RARP request, and 4 for RARP reply.
Sender Hardware Address
Sender's hardware address.
Sender Protocol Address
Sender's protocol address.
Target Hardware Address
Hardware address for the recipient. Requests disregard this field. When sending a request message, the entire Target Hardware Address is set to zero.
Target Protocol Address
Protocol address for the recipient.