Methods Used by the Extended DHCP Local Server to Determine Which Address-Assignment Pool to Use
You can specify the method that the extended DHCP local server uses to determine which address-assignment pool provides the IP address and configuration for a DHCP client. By default, the server matches the IP address in the client DHCP request to the address of the address-assignment pool.
The following sections describe the methods used by the DHCP local server to determine which address-assignment pool to use:
Matching the Client IP Address to the Address-Assignment Pool
In the default configuration, the server selects the address-assignment pool to use by matching the IP address in the client DHCP request with the network address of the address-assignment pool. If the client request contains the gateway IP address (giaddr), the local server matches the giaddr to the address-assignment pool’s address. If there is no giaddr in the request, the DHCP local server matches the IP address of the receiving interface to the address of the address-assignment pool.
Matching Option 82 Information to Named Address Ranges
You can also configure the extended DHCP local server to match the DHCP relay agent information option (option 82) in the client DHCP packets to a named range in the address-assignment pool used for the client. Named ranges are subsets within the overall address-assignment pool address range, and are configured when you create the address-assignment pool. To use the DHCP local server option 82 matching feature, you must ensure that the option-82 statement is included in the dhcp-attributes statement for the address-assignment pool.
 | Note: To enable the option 82 matching method, you must first specify the ip-address-first statement in the pool-match-order statement, and then specify the option-82 statement. |
