3Com SuperStack 3 3250 Implementation Manual page 95

Figure 25 Example of an ARP Cache
ARP cache
IP address
158.101.1.1
158.101.2.1
If the IP address does not have a corresponding MAC address, the host or
router broadcasts an ARP request packet to all the devices on the
network. The ARP request contains information about the target and
source addresses for the protocol (IP addresses). See
Figure 26 Example of an ARP Request Packet
00802322b00ad
158.101.2.1
?
158.101.3.1
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 exchanges both source and target
fields. This packet is then sent back to the source device.
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 27.
MAC address
00308e3d0042
0080232b00ab
Source hardware address
Source protocol address
Target hardware address
Target protocol address
IP Routing Protocols
Figure 26.
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