Proxy ARP and Local Proxy ARP

Overview

Proxy ARP (RFC 1027) is a technique by which a device on a given network answers the ARP queries for a network address that is not on that network. The Proxy ARP is aware of the location of the traffic's destination, and offers its own MAC address as destination. The captured traffic is then typically routed by the Proxy to the intended destination via another interface. Proxy ARP can help machines on a subnet reach remote subnets without the need to configure routing or a default gateway.

Use no ip proxy-arp to disable Proxy ARP, Proxy ARP is disabled by default.

Topology

Figure 79. Sample topology

Host A

Table 80.  

#configure terminal	Enter Configure mode.
(config)#interface xe1	Specify the interface to be configured on Host A
(config-if)#ip address 20.20.0.3/24	Configure the ip address on the interface
(config)#commit	Commit the candidate configuration to the running configuration
(config)#end	Exit interface and configure mode

Host B

#configure terminal	Enter Configure mode
(config)#interface xe1	Specify the interface to be configured on Host B
(config-if)#ip address 20.20.1.2/24	Configure the ip address on the interface
(config)#commit	Commit the candidate configuration to the running configuration
(config)#end	Exit interface and configure mode

Enable Proxy ARP

#configure terminal	Enter Configure mode.
(config)#interface xe1	Specify the interface connected to Host A
(config-if)#ip address 20.20.0.1/24	Configure the ip address on the interface
(config-if)#interface xe2	Specify the interface connected to Host B
(config-if)#ip address 20.20.1.1/24	Configure the ip address on the interface
(config-if)#interface xe1	Specify the interface to configure Proxy ARP
(config-if)#ip proxy-arp	Enable Proxy ARP
(config)#commit	Commit the candidate configuration to the running configuration
(config)#end	Exit interface and configure mode

Validation

The show arp command on the hosts shows the ARP table entries to reach different subnets. Ping Host A from Host B. The ARP table should have the router’s xe1 interface MAC address to reach Host A. Execute the below command at Host B: