H3C Technologies H3C SecBlade NetStream Cards - Manual (Page 128)

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ARP configuration
This chapter includes these sections:
• ARP overview
• Configuring ARP
• Displaying and maintaining ARP
• ARP configuration example
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, a device uses ARP to resolve the IP address of the next hop to the corresponding
MAC address.
ARP message format
ARP messages are classified into ARP requests and ARP replies. Figure 37 shows the format of the ARP
request/reply. Numbers in the figure refer to field lengths.
Figure 37 ARP message format
ARP message fields:
• Hardware type: The hardware address type. The value 1 represents Ethernet.
• Protocol type: The type of the protocol address to be mapped. The hexadecimal value 0x0800
represents IP.
• Hardware address length and protocol address length: Length, in bytes, 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. The type of the ARP message. The value 1 represents an ARP request and 2
represents an ARP reply.
• Sender hardware address: Hardware address of the device sending the message.