3Com CoreBuilder 3500, Implementation Manual

Page: 287 / 592

Address Resolution Protocol (ARP) 287
Figure 54
Example of an ARP Request Packet
When devices on the network receive this packet, they examine it. If their
address is not the target protocol address, they discard the packet. When
a device receives the packet and confirms that its IP address matches the
target protocol address, the receiving device places its MAC address in
the target hardware address field and sends the packet back to the
source hardware address. When the originating host or router receives
this
ARP reply , it places the new MAC address in its ARP cache next to the
corresponding IP address. See Figure 55.
Figure 55
Example of ARP Cache Updated with ARP Reply
After the MAC address is known, the host or router can send the packet
directly to the next hop.
158.101.3.1
158.101.2.1
Source hardware address
?
ARP request packet
Source protocol address
Target protocol address
Target hardware address
00802322b00ad
ARP cache
158.101.1.1
158.101.2.1
158.101.3.1
IP address MAC address
00308e3d0042
0080232b00ab
0134650f3000