
Configuring Address Resolution
117356-A Rev. A 5-9
Enabling Proxy ARP on an Interface
Proxy ARP allows a router to answer a local ARP request for a remote destination.
For example, in Figure 5-
2, Hosts B and C are located on the same network but on
separate subnetworks. Hosts B and C do not understand subnetworking. The
router connecting the two physical networks knows which host resides on which
network. The address mask is 255.255.255.000. In this example, one subnet is a
remote network with respect to the other subnet.
Figure 5-2. Proxy ARP Example
Host B wants to talk to Host C, so Host B broadcasts an ARP request, which asks
IP address 140.250.250.3 to respond with its physical address. The router captures
Host B’s ARP request and responds with its hardware address 00 002 00 00 01
and Host C’s IP address 140.250.250.3. Host B maps Host C’s IP address
140.250.250.3 to the router’s hardware address 00 002 00 00 01.
140.250.250.0140.250.200.0
140.250.250.2140.250.200.2
140.250.200.1
00 002 00 00 01
140.250.200.1
00 002 00 00 01
140.250.250.3140.250.250.3
00 002 00 10 600 002 00 10 30
Router
Host
C
Host
A
Host
A
Host
B
IP0011A
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