ARP-to-host conversion

1. Introduction
Enable ARP-to-host conversion on a specified interface. If the interface is a Layer-3
interface in Up status, ARP entries will be converted into 32-bit host routes on the
interface.

2. Scenario

In special requirement scenarios, communication is required between hosts, but ARP packets sent by hosts are not desired to transmit across the whole network. In this case, you can run the arp-to-host command on the devices connected to hosts to convert ARP entries to host routes, so that the remote devices learn the host routes through BGP redistribution to meet the scenario requirement.

As shown in the following figure, PC1 and PC2 are two hosts in the same network segment. PC1 and PC2 are required to communicate with each other, but ARP packets are not desired to transmit across the whole network. Run the arp-to-host command on R1 and R2 to generate ARP host routes, establish a BGP peer relationship between R1 and R2, and enable ARP host route redistribution. In this case, both R1 and R2 can obtain routes to PC1 and PC2 to implement network interconnection.

3. Configuring ARP-to-host Conversion

1) Overview

If other routing protocols are needed to distribute the direct route or instruct forwarding

routes, the information in ARP table can be converted into host routes, and then

redistributed by other routing protocols.

2) Restrictions and Guidelines

• This function cannot be configured on a Layer-2 switch.
• The interface must be a Layer-3 interface in Up status.

3) Configuring the Interface to Enable ARP-to-host Conversion

(1) Enter the privileged EXEC mode.

privilege

(2) Enter the global configuration mode.

config-system terminal

(3) Enable ARP-to-host conversion on a specified interface.

ip route-config arp-to-host interface interface-type interface-number

The ARP-to-host conversion function is disabled on an interface by default.

4) Configuring BGP Redistributed ARP-host Route

(1) Enter the privileged EXEC mode.

privilege

(2) Enter the global configuration mode.

config-system terminal

(3) Enter the BGP configuration mode.

router-protocol bgp as-number

(4) Configure BGP redistributed ARP-host route.

Redistribute-route arp-host

ARP-host routes are not redistributed by default.