
Customizing IP Services
114065 Rev. A 3-27
Configuring Address Resolution
The IP router needs both a physical address and an IP address to transmit a
datagram. In situations where the router knows only the network host’s IP address,
the Address Resolution Protocol (ARP) enables the router to determine a network
host’s physical address by binding a 32-bit IP address to a 48-bit MAC address. A
router can use ARP across a single network only, and the network hardware must
support physical broadcasts.
Figure 3-4. ARP Example
For example, in Figure 3-4, the router and Host C are on the same physical
network. Both devices have an assigned IP address (the router’s is 140.250.200.1
and Host C’s is 140.250.200.4) and both devices have an assigned physical
address (the router’s is 00 00 A2 00 00 01 and Host C’s is 00 00 A2 00 10 40).
140.250.200.0
140.250.200.1
00 00A2 00 00 01
140.250.200.2
00 00A2 00 10 20
140.250.200.3
00 00A2 00 10 30
140.250.200.4
00 00A2 00 10 40
Router
Host
C
Host
A
Host
B
IP0010A
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