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CLI-based Configuration Guide - Security

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

This document provides the basic concepts, configuration procedures, and configuration examples in different application scenarios of the network management feature supported by the device.
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Configuring Defense Against Bogus DHCP Message Attacks

Configuring Defense Against Bogus DHCP Message Attacks

Context

If an attack pretends to be an authorized user to send a bogus DHCP message to the DHCP server on a DHCP network, the authorized user cannot use the IP address or goes offline unexpectedly. After the DHCP snooping binding table is generated, the device can check DHCP messages against the binding table. Only messages that match the binding table can be forwarded; otherwise, the messages are discarded. This prevents unauthorized users from sending bogus DHCP messages to renew or release IP addresses.

Procedure

  1. Enable a device to check DHCP messages against the DHCP snooping binding table.

    If the function is configured in the VLAN view, it takes effect on all the interfaces in the VLAN; if the function is configured in the interface view, it takes effect only on the interface.

    1. Run system-view

      The system view is displayed.

    2. Run vlan vlan-id or interface interface-type interface-number

      The VLAN or interface view is displayed, respectively.

    3. Run dhcp snooping check user-bind enable

      The device is enabled to check DHCP messages against the DHCP snooping binding table.

      By default, a device is not enabled to check DHCP messages against the DHCP snooping binding table.

    4. Run dhcp snooping check mac-address enable

      The function of checking whether the CHADDR field is the same as the source MAC address of the header of a DHCP Request message is enabled.

      By default, the function of checking whether the CHADDR field is the same as the source MAC address of the header of a DHCP Request message is disabled.

  2. (Optional) Enable the DHCP snooping alarm function.
    1. Run system-view

      The system view is displayed.

    2. Run interface interface-type interface-number

      The interface view is displayed.

    3. Run dhcp snooping alarm { user-bind | mac-address | untrust-reply } enable

      The DHCP snooping alarm function is enabled.

      By default, the DHCP snooping alarm function is disabled.

  3. (Optional) Configure the alarm threshold.

    The alarm threshold can be set both in the system view and interface view. If the alarm threshold is configured in the system view and interface view, the smaller value takes effect.

    • In the system view:

    1. Run system-view

      The system view is displayed.

    2. Run dhcp snooping alarm threshold threshold

      The alarm threshold for the number of DHCP snooping-discarded messages is configured.

      If this command is run in the system view, it takes effect on all the interfaces of the device.

      By default, the alarm threshold for the number of DHCP snooping-discarded messages is 100.

    • In the interface view:

    1. Run system-view

      The system view is displayed.

    2. Run interface interface-type interface-number

      The interface view is displayed.

    3. Run dhcp snooping alarm { user-bind | mac-address | untrust-reply } threshold threshold

      The alarm threshold for the number of DHCP snooping-discarded messages is configured.

      By default, the global alarm threshold for the number of DHCP snooping-discarded messages is 100, and the alarm threshold for the number of DHCP snooping-discarded messages on an interface is the value configured using the dhcp snooping alarm threshold command in the system view.

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Updated: 2019-05-20

Document ID: EDOC1100034236

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