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Configuration Guide - IP Service

CloudEngine 8800, 7800, 6800, and 5800 V200R003C00

This document describes the configurations of IP Service, including IP address, ARP, DHCP, DNS, IP performance optimization, IPv6, DHCPv6, and IPv6 DNS.
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Configuring Proxy ARP Anyway

Configuring Proxy ARP Anyway

Context

In scenarios where servers are partitioned into VMs, to allow flexible deployment and migration of VMs on multiple servers or switches, the common solution is to configure Layer 2 interconnection between multiple switches. However, this approach may lead to larger Layer 2 domains on the network and the risk of broadcast storms. To resolve this problem, the common method is to configure a VM gateway on an access switch and enable proxy ARP anyway on the gateway so that the gateway sends its own MAC address to a source VM and communication between VMs is implemented through route forwarding.

As shown in Figure 2-11, the IP address of VM1 is 10.10.10.1/24 and the IP address of VM2 is 10.10.10.4/24. VM1 and VM2 are on the same network segment. The two networks are connected through the VLANIF 10 interfaces with the same IP address and MAC address on Switch1 and Switch2, respectively. The IP addresses of VM1 and VM2 are on the same network segment. When VM1 needs to communicate with VM2, it broadcasts an ARP Request packet, requesting the MAC address of VM2. However, VM1 and VM2 are on different physical networks (in different broadcast domains). VM2 cannot receive the ARP Request packet sent from VM1 and does not respond with an ARP Reply packet.
Figure 2-11 Proxy ARP anyway implementation

To resolve this problem, you can enable proxy ARP anyway on the VLANIF 10 interfaces on Switch1 and Switch2.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run interface interface-type interface-number

    The interface view is displayed.

  3. On an Ethernet interface, run undo portswitch

    The interface is switched to Layer 3 mode.

    By default, an Ethernet interface works in Layer 2 mode.

    The mode switching function takes effect when the interface only has attribute configurations (for example, shutdown and description configurations). Alternatively, if configuration information supported by both Layer 2 and Layer 3 interfaces exists (for example, mode lacp and lacp system-id configurations), no configuration that is not supported after the working mode of the interface is switched can exist. If unsupported configurations exist on the interface, delete the configurations first and then run the undo portswitch command.

    NOTE:

    If many Ethernet interfaces need to be switched to Layer 3 mode, run the undo portswitch batch interface-type { interface-number1 [ to interface-number2 ] } &<1-10> command in the system view to switch these interfaces to Layer 3 mode in batches.

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

    IP addresses are configured for interfaces.

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

  5. Run arp proxy anyway enable

    Proxy ARP anyway is enabled on the interface.

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

    After proxy ARP anyway is enabled, the aging time of ARP entries on servers 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.

  6. Run commit

    The configuration is committed.

Follow-up Procedure

  • On an interface for which proxy ARP anyway is configured, you need to run the arp direct-route enable command to advertise host routes generated based on ARP entries.

  • After the proxy ARP anyway function is enabled, broadcasting outgoing ARP request packets needs to be blocked.
    • If only ARP request packets need to be broadcast, run the storm suppression broadcast block outbound command on the physical interface where proxy ARP anyway is enabled to block outgoing broadcast packets. For example, if proxy ARP anyway is enabled on a VLANIF interface, run the storm suppression broadcast block outbound command on the VLAN member interface corresponding to the VLANIF interface.
    • If other packets in addition to ARP request packets need to be broadcast, configure an MQC traffic policy to block the broadcast of outgoing ARP request packets and allow other packets to be broadcast.
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Updated: 2019-05-08

Document ID: EDOC1100004354

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