Configuring Proxy Arp; Overview; Common Proxy Arp; Local Proxy Arp - HP 10500 Series Configuration Manual

Configuring proxy ARP

Overview

Proxy ARP enables a device on a network to answer ARP requests for an IP address not on that network.
With proxy ARP, hosts on different broadcast domains can communicate with each other as they do on
the same network.
Proxy ARP includes common proxy ARP and local proxy ARP.
Common proxy ARP—Allows communication between hosts that connect to different Layer-3
•
interfaces and reside in different broadcast domains.
Local proxy ARP—Allows communication between hosts that connect to the same Layer-3 interface
•
and reside in different broadcast domains.

Common proxy ARP

A proxy ARP enabled device allows hosts that reside on different subnets to communicate.
As shown in
The IP addresses of the two VLAN-interfaces are 192.168.10.99/24 and 192.168.20.99/24. Host A and
Host B are assigned the same prefix 192.168.0.0. Host A connects to VLAN-interface 1 and Host B
connects to VLAN-interface 2.
Figure 7 Application environment of proxy ARP
Because Host A and Host B have the same prefix 192.168.0.0, Host A considers that Host B is on the
same network, and it broadcasts an ARP request for the MAC address of Host B. However, Host B cannot
receive this request because it is in a different broadcast domain.
You can enable proxy ARP on VLAN-interface 1 of the switch so that the switch can reply to the ARP
request from Host A with the MAC address of VLAN-interface 1 and forward packets sent from Host A to
Host B. In this case, the switch acts as a proxy of Host B.
A main advantage of proxy ARP is that you can enable it on a single device without disturbing routing
tables of other devices in the network. Proxy ARP acts as the gateway for hosts that are not configured
with a default gateway or do not have routing capability.

Local proxy ARP

As shown in
to GigabitEthernet 1/0/3 while Host B connects to GigabitEthernet 1/0/1. Enable local proxy ARP on
Switch A to allow Layer 3 communication between the two hosts.
Figure 7, Switch connects to two subnets through VLAN-interface 1 and VLAN-interface 2.
Figure 8, Host A and Host B belong to VLAN 2, but are isolated at Layer 2. Host A connects
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