Arp Configuration; Arp Overview; Arp Function; Arp Message Format - HP A7500 Series Configuration Manual

ARP configuration

NOTE:
You can use the port link-mode command to set an Ethernet port to operate in bridge (Layer 2) or route
mode (Layer 3) (see

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 include ARP requests and ARP replies.
Numbers in the figure refer to field lengths.
Figure 1 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. 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.
•
Sender protocol address: Protocol address of the device sending the message.
•
• Target hardware address: Hardware address of the device the message is being sent to.
Layer 2—LAN Switching Configuration Guide
).
Figure 1 shows the format of the ARP request/reply.
1