Configuration guidelines
Follow these guidelines when you enable the DHCP server on an interface:
If a DHCP relay agent exists between the DHCP server and client, the DHCP server, regardless of whether the subaddress keyword is used, selects an IP address from the address pool containing the primary IP address of the DHCP relay agent's interface (connected to the client) for a requesting client.
When the DHCP server and client communicate without Layer 3 forwarding:
With the keyword subaddress specified, the DHCP server will preferably assign an IP address from an address pool that resides on the same subnet as the primary IP address of the server interface (connecting to the client). If the address pool contains no assignable IP address, the server assigns an IP address from an address pool that resides on the same subnet as the secondary IP addresses of the server interface. If the interface has multiple secondary IP addresses, each address pool is tried in turn for address allocation. If the interface has no secondary IP addresses, the server is unable to assign an IP address to the client.
Without the keyword subaddress specified, the DHCP server can only assign an IP address from the address pool that resides on the same subnet as the primary IP address of the server interface.