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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 Defense Against Bogus DHCP Message Attacks

Configuring Defense Against Bogus DHCP Message Attacks

Context

If an attacker sends a bogus DHCP Request message to the DHCP server to extend the lease, the IP address cannot be released after the lease expires and authorized users cannot use the IP address. If the attacker forges a DHCP Release message of an authorized user and sends it to the DHCP server, the authorized user may be disconnected.

After a DHCP snooping binding table is generated, the device checks DHCP Request and Release messages against the binding table. Only DHCP messages that match entries are forwarded. This prevents unauthorized users from sending bogus DHCP Request messages or Release messages to extend the lease or to release IP addresses.

Procedure

  1. Run system-view

    The system view is displayed.

  2. You can enable the device to check the DHCP messages against the binding table in the system view, VLAN view, or interface view.

    • In the system view:

    1. Run dhcp snooping check vlan { vlan-id1 [ to vlan-id2 ] }&<1-10>

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

      By default, the device does not check DHCP messages against the DHCP snooping binding table.

    • In the VLAN view or interface view:

    1. Run vlan vlan-id

      The VLAN view is displayed.

      Or run interface interface-type interface-number

      The interface view is displayed.

    2. Run dhcp snooping check

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

      By default, the device does not check DHCP messages against the DHCP snooping binding table.

      NOTE:

      If you run this command in the VLAN view, the command takes effect on all the DHCP messages in the specified VLAN received by all the interfaces on the device.

    3. Run quit

      Return to the system view.

  3. Enable the trap function for DHCP snooping in the interface view.
    1. Run interface interface-type interface-number

      The interface view is displayed.

    2. Run dhcp snooping alarm binding enable

      An alarm is generated when the number of DHCP messages that are discarded because they do not match DHCP snooping binding entries reaches the threshold.

      By default, the trap function for discarded DHCP messages is disabled.

    3. Run quit

      Return to the system view.

  4. (Optional) Set the alarm threshold for the number of messages discarded by DHCP snooping in the system view or interface view.

    • In the system view:

    1. Run dhcp snooping alarm threshold threshold

      The alarm threshold for the number of discarded messages by DHCP snooping is set.

      If you run this command in the system view, the command takes effect for all the interfaces on the device.

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

    • In the interface view:

    1. Run interface interface-type interface-number

      The interface view is displayed.

    2. Run dhcp snooping alarm binding threshold threshold

      The alarm threshold for the number of messages discarded because they do not match the DHCP snooping binding entries is set.

      By default, an alarm is generated in the system when at least 100 DHCP snooping messages are discarded, and the alarm threshold on an interface is set using the dhcp snooping alarm threshold command in the system view.

  5. Run commit

    The configuration is committed.

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Updated: 2019-04-20

Document ID: EDOC1100074765

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