Arp Configuration; Arp Overview; Arp Function; Arp Message Format - H3C S5120-SI Series Configuration Manual

ARP configuration

ARP overview

ARP function

ARP is used to resolve an IP address into a physical address, such as an Ethernet MAC address.
In an Ethernet LAN, when a device sends data to another device, it uses ARP to translate the destination
IP address to the corresponding MAC address.

ARP message format

ARP messages include ARP requests and ARP replies. Figure 1 shows the ARP message format.
Figure 1 ARP message format
The following explains the fields in Figure 1.
•
Hardware type: This field specifies the hardware address type. The value "1" represents Ethernet.
•
Protocol type: This field specifies the type of the protocol address to be mapped. The hexadecimal
value "0x0800" represents IP.
•
Hardware address length and protocol address length: They respectively specify the length of a
hardware address and a protocol address, in bytes. For an Ethernet address, the value of the
hardware address length field is "6". For an IP(v4) address, the value of the protocol address length
field is "4".
•
OP: Operation code. This field specifies the type of ARP message. The value "1" represents an ARP
request and "2" represents an ARP reply.
•
Sender hardware address: This field specifies the hardware address of the device sending the
message.
•
Sender protocol address: This field specifies the protocol address of the device sending the message.
•
Target hardware address: This field specifies the hardware address of the device the message is
being sent to.
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