The server then replies with a DHCPACK to finish the DHCP session.
his option is used in DHCPOFFER and DHCPREQUEST messages, and may optionally be included in the DHCPACK and DHCPNAK messages. DHCP servers include this option in the DHCPOFFER in order to allow the client to distinguish between lease offers. DHCP clients use the contents of the 'server identifier' field as the destination address for any DHCP messages unicast to the DHCP server. DHCP clients also indicate which of several lease offers is being accepted by including this option in a DHCPREQUEST message. The identifier is the IP address of the selected server.
This option is used in a client request (DHCPDISCOVER or DHCPREQUEST) to allow the client to request a lease time for the IP address. In a DHCPOIFFER server reply, a DHCP server uses this option to specify the lease time it is willing to offer. The time is in units of seconds, and is specified as a 32-bit unsigned integer.
The subnet mask option specifies the client's subnet mask as per RFC 950. If both the subnet mask and the router option are specified in a DHCP reply, the subnet mask option must be first.
This option specifies the broadcast address in use on the client's subnet.
The router option specifies a list of IP addresses for routers on the client's subnet. Routers should be listed in order of preference.
The domain name server option specifies a list of Domain Name System name servers available to the client. Servers should be listed in order of preference.