Arp Address Resolution Process - H3C S9500 Series Operation Manual

Operation Manual – ARP
H3C S9500 Series Routing Switches
Hardware type: This field specifies the type of a hardware address. The value "1"
represents an Ethernet address.
Protocol type: This field specifies the type of the protocol address to be mapped.
The hexadecimal value "0x0800" represents an IP address.
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.
Target protocol address: This field specifies the protocol address of the device the
message is being sent to.

1.1.3 ARP Address Resolution Process

Figure 1-2 ARP address resolution process
Suppose that Host A and Host B are on the same subnet and that Host A sends a
message to Host B. The resolution process is as follows:
1) Host A looks in its ARP mapping table to see whether there is an ARP entry for
Host B. If Host A finds it, Host A uses the MAC address in the entry to encapsulate
the IP packet into a data link layer frame and sends the frame to Host B.
2) If Host A finds no entry for Host B, Host A buffers the packet and broadcasts an
ARP request, in which the source IP address and source MAC address are
respectively the IP address and MAC address of Host A and the destination IP
address and MAC address are respectively the IP address of Host B and an
Host A
192.168.1.1
0002.6779.0f4c
Sender MAC Sender IP
address
0002.6779.0f4c 192.168.1.1
Sender MAC Sender IP
address
00a0.2470.febd
192.168.1.2
Target MAC
address
address
0000.0000.0000
Target MAC
address address
0002.6779.0f4c
1-2
Chapter 1 ARP Configuration
Host B
192.168.1.2
00a0.2470.febc
Target IP
address
192.168.1.2
Target IP
address
192.168.1.1