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DES-7200 Configuration Guide Chapter 4 DHCP Configuration
4-10
4.5.3.10 Configuring DHCP Address
Pool to Allocate Address as
per Option82
Generally, the DHCP relay agent will insert an option of "Option 82" to carry
relevant information about the client during the process of packet forwarding
(such as the VLAN to which the client belongs, slot number, port number or
user's 1X class). Upon receipt of such packets, the DHCP server will allocate
addresses according to the specific information about clients by analyzing
Option 82 information. For example, Option 82 can be utilized to allocate a
certain range of IP addresses to clients belonging to a certain VLAN or user
class. This feature can be used when it is needed to allocate a specific range of
IP addresses according to user's network allocation information (such as VLAN,
slot number or port number) or user's priority.
Each DHCP address pool can allocate addresses using Option 82 information.
Option 82 information will be matched and classified, and we can specify the
allocable address range for the corresponding class. One DHCP address pool
can be associated with multiple classes, and different address ranges can be
specified for each class.
During the process of address allocation, we can first determine the allocable
address pool according to the network segment to which the client belongs, and
then further determine its CLASS according to Option 82 information, so as to
allocate IP address from the address range corresponding to the CLASS. When
a request packet matches multiple classes in the address pool, address will be
allocated from the address ranges corresponding to these classes in the order
that the classes are configured in the address pool. If the class has not allocable
address, the address range for next matching class will be used, and the like.
Each class corresponds to one address range, and the addresses must be
allocated from low to high. Multiple classes can be configured with the same
address range. If the class associated with the address pool is specified but the
corresponding network scope is not configured, then the default address range
of this class shall be same as that of the address pool to which this class
belongs.
To configure the CLASS associated with address pool and the address range
corresponding to the class, execute the following commands in address pool
configuration mode:
Command Function
DES-7200(dhcp-config)# class
class-name
Configure the name of associated class,
and enter the class configuration mode
of address pool.