IP address allocation sequence

The DHCP server selects an IP address for a client in the following sequence:

1. IP address statically bound to the client's MAC address or ID.

2. IP address that was ever assigned to the client.

3. IP address designated by the Option 50 field in the DHCP-DISCOVER message sent by the client.

   Option 50 is the Requested IP Address option. The client uses this option to specify the wanted IP address in a DHCP-DISCOVER message. The content of Option 50 is user defined.

4. First assignable IP address found in the way discussed in "DHCP address assignment mechanisms" and "Principles for selecting an address pool."

5. IP address that was a conflict or passed its lease duration. If no IP address is assignable, the server does not respond.

   	NOTE: If a client moves to another subnet, the DHCP server selects an IP address in the address pool matching the new subnet. It does not assign the IP address that was once assigned to the client. Conflicted IP addresses can be assigned to other DHCP clients only after the addresses are in conflict for an hour.