55 PROXY ARP CONFIGURATIONProxy ARP Overview Proxy ARP allows hosts that have IP addresses of the same network segment butreside on different physical networks to communicate with each other throughARP.Figure 148 Work mechanism of proxy ARPAs shown in Figure 148:From the perspective of the switch, Host A and Host D reside on differentnetworks. However, when Host A (192.168.0.22/16) needs to send packets toHost D (192.168.1.30/16), it finds they are on the same network 192.168.0.0/16,and thus Host A will broadcast an ARP request to request the MAC address ofHost D.■ When the proxy ARP feature is not enabled on the switch, because Host A andHost D are in different VLANs, the ARP request sent by Host A cannot reachHost D, and the two hosts cannot communicate.■ With proxy ARP enabled on the switch, when VLAN-interface 3 receives theARP request, if the switch finds a route to the destination IP address(encapsulated in the ARP request) in the routing table, the switch sends host Athe MAC address (00-00-0e-12-33-33) of VLAN-interface 3 in an ARP response(with the source IP address being the destination IP address of the ARPrequest). After receiving the ARP response, Host A creates an ARP entry, inwhich the destination IP address is the IP address of Host D (192.168.1.30/16),and the MAC address is that of VLAN-interface 3 (00-00-0e-12-33-33). Thesubsequent packets sent from Host A to Host D will all be sent to192.168.0.22/1600-00 -0e-12 -33-34Host A192 .168.1.29/1600 -00-0 e-14-34 -34Host BHost C Host D192.168.0.23/1600-00-0 e-12-33 -35192 .168.1.30/1600 -00-0 e-14-34 -35Vlan -int3192 .168 .0.27 /2400-00 -0e-12 -33-33Vlan -int4192 .168 .1.27 /2400 -00-0e -14-34 -33Switch
