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Configuring a DHCP client ID for an interface
About DHCP client ID
A DHCP client ID is added to the DHCP option 61 to uniquely identify a DHCP client. A DHCP server
can assign IP addresses to clients based on their DHCP client IDs.
DHCP client ID includes an ID type and a type value. Each ID type has a fixed type value. You can
specify a DHCP client ID by using one of the following methods:
• Use an ASCII string as the client ID. If an ASCII string is used, the type value is 00.
• Use a hexadecimal number as the client ID. If a hexadecimal number is used, the type value is
the first two characters in the number.
• Use the MAC address of an interface to generate a client ID. If this method is used, the type
value is 01.
The type value of a DHCP client ID can be displayed by the
display dhcp server ip-in-use
or
display dhcp client command.
Restrictions and guidelines
Make sure the ID for each DHCP client is unique.
Procedure
1. Enter system view.
system-view
2. Enter interface view.
interface interface-type interface-number
3. Configure a DHCP client ID for the interface.
dhcp client identifier { ascii ascii-string | hex hex-string | mac
interface-type interface-number }
By default, an interface generates the DHCP client ID based on its MAC address. If the
interface has no MAC address, it uses the MAC address of the first Ethernet interface to
generate its client ID.
Enabling duplicated address detection
About duplicated address detection
DHCP client detects IP address conflict through ARP packets. An attacker can act as the IP address
owner to send an ARP reply. The spoofing attack makes the client unable to use the IP address
assigned by the server. As a best practice, disable duplicate address detection when ARP attacks
exist on the network.
Procedure
1. Enter system view.
system-view
2. Enable duplicate address detection.
dhcp client dad enable
By default, the duplicate address detection feature is enabled on an interface.
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