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 15-22: Sample topology
Configuration
Host A
#configure terminal | Enter configure mode |
(config)#interface xe1 | Enter interface mode |
(config-if)#ip address 20.20.0.2/24 | Assign an IPv4 address to the interface |
(config)#end | Exit interface and configure mode |
Host B
#configure terminal | Enter configure mode |
(config)#interface xe1 | Enter interface mode |
(config-if)#ip address 20.20.1.2/24 | Assign an IPv4 address to the interface |
(config)#end | Exit interface and configure mode |
Proxy ARP Server
#configure terminal | Enter configure mode |
(config)#interface xe1 | Enter interface mode |
(config-if)#ip address 20.20.0.1/24 | Assign an IPv4 address to the interface |
(config-if)#ip proxy-arp | Enable proxy ARP |
(config-if)#exit | Exit interface mode |
(config-if)#interface xe2 | Enter interface mode |
(config-if)#ip address 20.20.1.1/24 | Assign an IPv4 address to the interface |
(config)#end | Exit interface and configure mode |
Validation
#show running-config arp
!
interface xe1
ip proxy-arp
!
The show arp command on the hosts shows the ARP table entries to reach different subnets. Ping Host B from Host A. The ARP table should have router’s xe1 interface MAC address to reach Host B. Execute the command at Host A.
#show arp
Address HWaddress Interface Type
20.20.0.2 52:54:00:24:43:23 eth1 Dynamic
192.168.52.1 fe:54:00:0d:1e:dc eth0 Dynamic
Last modified date: 07-14-2023