112
Step Command
Remarks
2.
Disable the DHCP
server from
encapsulating
Option 60 in DHCP
replies.
dhcp server reply-exclude-option60
By default, the DHCP server can
encapsulate Option 60 in DHCP
replies.
Configuring the DHCP server security features
Restrictions and guidelines
The DHCP server security features are not applicable if a DHCP relay agent exists in the network.
This is because the MAC address of the DHCP relay agent is encapsulated as the source MAC
address in the DHCP request received by the DHCP server. In this case, you must configure the
DHCP relay agent security features. For more information, see "
Configuring the DHCP relay agent
."
If you execute both the
dhcp flood-protection enable
and
dhcp server check mac-address
commands on an interface, the
dhcp server check mac-address
command takes effect.
Configuring DHCP flood attack protection
About DHCP flood attack protection
The DHCP flood attack protection enables the DHCP server to detect DHCP flood attacks according
to the DHCP packet rate threshold on a per-MAC basis.
When the DHCP server receives a DHCP packet from a client (MAC address), it creates a DHCP
flood attack entry in check state. If the number of DHCP packets from the same MAC address
reaches the upper limit in the detection duration, the server determines that the client is launching a
DHCP flood attack. The DHCP flood attack entry changes to the restrain state, and the DHCP server
discards the DHCP packets from that client. When the aging time of the entry is reached, the DHCP
server deletes the entry. If a DHCP packet from the MAC address arrives later, the DHCP server will
create a flood attack entry and count the number of incoming DHCP packets for that client again.
Procedure
To configure DHCP flood attack protection:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
(Optional) Set the DHCP
packet rate threshold for
DHCP flood attack detection.
dhcp flood-protection
threshold packet-number
milliseconds
By default, the device allows a
maximum of 6 DHCP packets per
5000 milliseconds from each
DHCP client.
3.
(Optional) Set the DHCP
flood attack entry aging time.
dhcp flood-protection
aging-time time
The default setting is 300
seconds.
4.
Enter interface view.
interface interface-type
interface-number
N/A
5.
Enable DHCP flood attack
protection.
dhcp flood-protection enable
By default, DHCP flood attack
protection is disabled.