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CLI-based Configuration Guide - IP Service

AR500, AR510, AR531, AR550, AR1500, and AR2500 V200R010

This document describes the concepts and configuration procedures of IP Service features on the device, and provides the configuration examples.

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Configuring Proxy ARP

Configuring Proxy ARP

The industrial switch router can function as a proxy of the destination host to reply an ARP Request message.

Pre-configuration Tasks

Before configuring proxy ARP, complete the following task:

  • Setting link layer protocol parameters for interfaces to ensure that the link layer protocol status of the interfaces is Up

Configuring Routed Proxy ARP

Context

Proxy ARP enables PCs or industrial switch routers on the same network segment but on different physical networks to communicate. In actual applications, if the current connected to the industrial switch router is not configured with a default gateway address (that is, the host does not know how to reach the intermediate system of the network), the host cannot forward data packets. Routed proxy ARP solves this problem.

Figure 2-8 shows the routed proxy ARP networking. RouterA uses GE1/0/0 and GE2/0/0 to connect two networks. IP addresses of the two GE interfaces are on different network segments. However, the masks make Host A and VLANIF10 on the same network segment, Host B and VLANIF20 on the same network segment, and Host A and Host B on the same network segment.

Figure 2-8  Networking diagram for configuring routed proxy ARP

HOST A sends an ARP Request packet, requesting the MAC address of HOST B. After receiving the packet, RouterA uses its MAC address to reply the Request packet. HOST A then forwards data using the MAC address of RouterA.

IP addresses of the STAhosts on a subnet have the same network ID. Therefore, the default gateway address does not need to be configured on the STAhosts.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run interface interface-type interface-number

    The interface view is displayed.

    The interfaces connect routing devices to the physical networks and are enabled with routed proxy ARP.

  3. Run ip address ip-address { mask | mask-length }

    IP addresses are configured for interfaces.

    The IP address configured for the interface enabled with routed proxy ARP must be on the same network segment as the IP address of the connected hostserver on a LAN.

  4. Run arp-proxy enable

    Routed proxy ARP is enabled on the interface.

    By default, routed proxy ARP is disabled on an interface.

    After proxy ARP is enabled, the aging time of ARP entries on hosts should be shortened so that invalid ARP entries can be deleted as soon as possible. The number of packets received but cannot be forwarded by the device is decreased. To set ARP aging time, run the arp expire-time expire-time command.

Checking the Configuration

After configuring routed proxy ARP is complete, run the following commands to check the configuration.

  • Run the display arp interface interface-type interface-number [ vid vlan-id [ cevid cevlan-id ] ] command to check ARP mapping entries of a specified interface.

  • Run the display arp vpn-instance vpn-instance-name [ dynamic | static ] command to check ARP mapping entries of a specified VPN instance.

Configuring Intra-VLAN Proxy ARP

Context

If two hosts belong to the same VLAN but are isolated, enable intra-VLAN proxy ARP on an interface associated with the VLAN to allow the hosts to communicate.

As shown in Figure 2-9, HOSTA and HOSTB connect to RouterA. The two interfaces that connect HOSTA and HOSTB to RouterA belong to VLAN10.

Figure 2-9  Intra-VLAN proxy ARP application

HOSTA and HOSTB cannot communicate at Layer 2 because interface isolation in a VLAN is configured on RouterA.

To solve this problem, enable intra-VLAN proxy ARP on the interfaces of RouterA. After an interface of RouterA receives an ARP Request packet whose destination address is not its own address, RouterA does not discard the packet but searches for the ARP entry. If the ARP entry matching HOSTB exists, RouterA sends its MAC address to HOSTA and forwards packets sent from HOSTA to HOSTB. RouterA functions as the proxy of HOSTB.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run interface interface-type interface-number

    The interface view is displayed.

  3. Run arp-proxy inner-sub-vlan-proxy enable

    Intra-VLAN proxy ARP is enabled.

    By default, intra-VLAN proxy ARP is disabled.

Checking the Configuration

After configuring intra-VLAN proxy ARP is complete, run the following commands to check the configuration.

  • Run the display arp interface interface-type interface-number [ vid vlan-id [ cevid cevlan-id ] ] command to check ARP mapping entries of a specified interface.

  • Run the display arp vpn-instance vpn-instance-name [ dynamic | static ] command to check ARP mapping entries of a specified VPN instance.

Configuring Inter-VLAN Proxy ARP

Context

If two hosts belong to different VLANs, enable inter-VLAN proxy ARP on interfaces associated with the VLANs to implement Layer 3 communication between the two hosts.

As shown in Figure 2-10, HOSTA and HOSTB connect to RouterA. Interfaces that connect HOSTA and HOSTB to RouterA belong to VLAN10 and VLAN20 respectively.

Figure 2-10  Inter-VLAN proxy ARP application

Interfaces connecting HOSTA and HOSTB to RouterA belong to different VLANs. Therefore, HOSTA and HOSTB cannot communicate at Layer 2.

To solve this problem, inter-VLAN proxy ARP needs to be enabled on interfaces of RouterA. After an interface of RouterA receives an ARP Request packet whose destination address is not its own address, RouterA does not discard the packet but searches for the ARP entry. If the ARP entry matching HOSTB exists, RouterA sends its MAC address to HOSTA and forwards packets sent from HOSTA to HOSTB. RouterA functions as the proxy of HOSTB.

Inter-VLAN proxy ARP implements the following functions:

  • Allows users in different VLANs to communicate at Layer 3.

  • Allows users in different sub-VLANs to communicate. You need to enable inter-VLAN proxy ARP on the VLANIF interface of the super-VLAN.

Procedure

  1. Run system-view

    Enter the system view.

  2. Run interface interface-type interface-number

    The interface view is displayed.

  3. Run arp-proxy inter-sub-vlan-proxy enable

    Inter-VLAN proxy ARP is enabled.

    By default, inter-VLAN proxy ARP or proxy ARP on termination sub-interfaces is disabled.

Checking the Configuration

After configuring inter-VLAN proxy ARP is complete, run the following commands to check the configuration.

  • Run the display arp interface interface-type interface-number [ vid vlan-id [ cevid cevlan-id ] ] command to check ARP mapping entries of a specified interface.

  • Run the display arp vpn-instance vpn-instance-name [ dynamic | static ] command to check ARP mapping entries of a specified VPN instance.

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Updated: 2019-05-20

Document ID: EDOC1100034231

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