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ARP Configuration
This chapter includes these sections:
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z
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Displaying and Maintaining ARP
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ARP Overview
ARP Function
The Address Resolution Protocol (ARP) is used to resolve an IP address into a physical address
(Ethernet MAC address, for example).
In an Ethernet LAN, when a device sends data to another device, it uses ARP to translate the IP
address of that device to the corresponding MAC address.
ARP Message Format
ARP messages are classified into ARP requests and ARP replies.
shows the format of the
ARP request/reply.
Figure 1-1
ARP message format
The following describe the fields in
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Hardware type: This field specifies the hardware address type. The value “1” represents Ethernet.
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Protocol type: This field specifies the type of the protocol address to be mapped. The
hexadecimal value “0x0800” represents IP.
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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”.
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OP: Operation code. This field specifies the type of the ARP message. The value “1” represents
an ARP request and “2” represents an ARP reply.
