What are the Most Common DHCP Options & their Functions?

What are DHCP and DHCP options in the current network infrastructure? This article breaks down everything about it. 

What is DHCP

Abbreviated as Dynamic Host Configuration Protocol, this tech enables automatically assigns an Internet Protocol host with its IP address and other necessary configuration data like the subnet mask and default gateway. The Internet Engineering Task Force defines DHCP as a standard based on the Bootstrap Protocol, a protocol with which it shares many implementation specifics. 

With DHCP, hosts may get the necessary TCP/IP setup data from a DHCP server. In the first stages of deploying network access, providing DHCP choices is a wise strategy to set up network clients. The DHCP protocol makes it possible to specify a sizable number of variables that are highly helpful for device configuration in addition to supplying the IP address.

How DHCP works?

To connect to a TCP/IP-based network and use its resources, each device needs a distinct unicast IP address. Without DHCP, it is necessary to manually assign IP addresses for new computers, computers that are transferred from one subnet to another, and computers that are withdrawn from the network.  

This entire procedure is mechanized and centralized with DHCP. Any DHCP-enabled client that joins the network receives a lease on an IP address from the DHCP server, which manages a pool of IP addresses. As opposed to static IP addresses, which are dynamic (leased) instead, addresses that are no longer in use are automatically returned to the pool for reallocation.

What is the DHCP Option?

You have control over the following features of routing in your virtual network thanks to different options of DHCP or options sets. There are many commonly used options are: The Network Time Protocol (NTP) servers, DNS servers, and domain names used by the equipment in your VPC are all within your control. 

Each option has a name and a number that will be sent in the protocol frames to identify it like router selection is Option 3 in which the gateway address that will be given to the customers is specified. DNS server choice is option 6 in which the IP address of the DNS server that will be given to the clients is specified. Static route option, or option 33 outlines the classful static routes that a client should add to its routing table. Classful static routes are those in which the destination addresses are classful. 

Option 14 is also there which is used to indicate that a two-message exchange will be utilized for address assignment. If the client is prepared to send a Solicit/Reply message exchange, the client may utilize this option in a Solicit message. During the Solicit/Reply message exchange, servers must provide this option in a Reply delivered in response to a Solicit. 

Another one associated with DHCPv6 is option 6 which is used whenever a message is sent between a client and a server. To let the server know what options the client wishes to receive, a client must include an "Option Request" option in a Solicit, Request, Renew, Rebind, or Information-request message.

All devices that request an IP address can get choices from DHCP servers that are configured to be tied to a particular client identity or Mac address family. Any client connecting to the network can request certain DHCP settings (such as vendor class, hostname, or login credentials) in addition to its IP address. The DHCP clients on the network are often identified from the list of choices requested. A relay agent that is transmitting a broadcasted request from the local network to a main DHCP server can also insert DHCP options.

Applications of DHCP and DHCP Options:

It provides dependable setting of IP addresses and reduces setup problems brought on by manual IP address setting, such as typos or address conflicts brought on by simultaneously assigning IP addresses to several computers. It also enables decreased network management by introducing a TCP/IP setting that is automated and centralized. Also, you get a central location from which to define TCP/IP setups.

Final Notes:

DHCP is a development of the BOOTP protocol, which was initially developed to bootstrap a diskless client. It should be noted that any client connecting to the network has the opportunity to request additional DHCP settings beyond just an IP address. In most cases, the network's DHCP clients are identified by the list of options they have requested. Last but not least, DHCP options may be added by a relay agent that is transmitting a local network broadcast request to a centralized DHCP server.