The Dynamic Host Configuration Protocol (DHCP) provides an administrator with a framework for passing configurations to DHCP clients on a network. DHCP Options are added configuration parameters that a DHCP server can hand out to DHCP clients. When the DHCP server receives the DHCP Request message from the client, the server (typically) responds by sending a DHCP ACK packet to the client. At this time, the server will forward any configured options within the DHCP ACK packet.
Option 3 (Gateway)
This option is used to tell the client which address is the default gateway.
Option 4 (Time Server)
This option is used to specify the time server available to the client. This is also related to the time zone offset option.
Option 12 (Hostname)
This option is used to carry the “hostname” portion of a node’s Fully Qualified Domain Name.
For example, “mail” of mail.meraki.com.
Option 15 (Domain Name)
This option is used to carry the “domain” portion of a node’s Fully Qualified Domain Name. For example, “meraki.com” of mail.meraki.com.
Option 42 NTP servers
This option carries the NTP servers used on the network.
Option 66 (TFTP Server)
This option is used to carry the IP address or hostname of a TFTP server.