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Configuration Guide - Security

CloudEngine 8800, 7800, 6800, and 5800 V200R005C10

This document describes the configurations of Security, including ACL, local attack defense, MFF, attack defense, traffic suppression and storm control, ARP security, Port security, DHCP snooping, ND snooping, PPPoE+, IPSG, SAVI, separating the management plane from the service plane, security risks.
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Configuring Strict ARP Learning

Configuring Strict ARP Learning

Context

If many user hosts simultaneously send a large number of ARP packets to a device, or attackers send bogus ARP packets to the device, the following problems occur:
  • Processing ARP packets consumes many CPU resources. The device learns many invalid ARP entries, which exhaust ARP entry resources and prevent the device from learning ARP entries for ARP packets from authorized users. Consequently, communication of authorized users is interrupted.
  • After receiving bogus ARP packets, the device incorrectly modifies the ARP entries. As a result, authorized users cannot communicate with one another other.

To avoid the preceding problems, configure the strict ARP learning function on the gateway. This function allows the gateway to learn only ARP entries for ARP Reply packets in response to ARP Request packets that it has sent. In this way, the gateway can prevent most ARP attacks.

Strict ARP learning can be configured globally or in the interface view.

  • If strict ARP learning is enabled globally, all interfaces on the device learn ARP entries strictly.
  • If strict ARP learning is enabled in the interface view, only this interface learns ARP entries strictly.

When strict ARP learning is enabled globally and in the interface view simultaneously, the configuration on the interface takes precedence over the global configuration.

NOTE:
When strict ARP learning is enabled globally:
  • If you run the arp learning strict force-disable command on a specified interface, strict ARP learning is forced to be disabled on the interface.
  • If you run the arp learning strict trust command on a specified interface, strict ARP learning configured globally takes effect on the interface.

Procedure

  • Configuring strict ARP learning globally
    1. Run system-view

      The system view is displayed.

    2. Run arp learning strict

      Strict ARP learning is enabled globally.

      By default, strict ARP learning is disabled.

    3. Run commit

      The configuration is committed.

  • Configuring strict ARP learning on an interface
    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 arp learning strict { force-enable | force-disable | trust }

      Strict ARP learning on the interface is enabled.

      By default, strict ARP learning is disabled on the interface.

    5. Run commit

      The configuration is committed.

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Updated: 2019-04-20

Document ID: EDOC1100074765

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