Overview of DHCP Option List & their Respective Functions

This article explains the most common ones from the DHCP option list and its basics as well. Let's start reading.

What is DHCP

DHCP is described as a standard by the Internet Engineering Task Force and is based on the Bootstrap Protocol, which it shares many implementation details with. It is a technology that permits the automated assignment of an Internet Protocol host's IP address as well as other relevant configuration information, such as the subnet mask and default gateway. The necessary TCP/IP configuration information may be obtained by hosts using DHCP from a DHCP server. 

This technology comprises of two network components: a network DHCP server that is deployed centrally and client instances of the protocol stack on each computer or device. This eliminates the necessity for manually configuring each network device separately. A client uses DHCP to make periodic requests to the server for a set of settings after connecting to the network.

DHCP option List

Multiple PCs, as well as other gadgets like mobile phones, tablets, and wireless printers, will receive IP addresses when DHCP is enabled. You might occasionally need to know a certain device's IP address or keep tabs on who is connected to your network. You may get this information from the DHCP Client List in either of these scenarios.

The devices and IP addresses issued by the server or router are simply listed in this client list. Every device that has a wired or wireless connection to the network is included in this list. You won't have access to this list if DHCP is disabled. Additionally, devices that are not network-connected won't show up on the list. Giving DHCP options is a smart way to set up this network with DHCP clients. In addition to providing the IP address, the DHCP protocol allows the specification of a significant number of factors that are very beneficial for device design. These are the most common in the options list are:

1. DHCP Option 1: Apply a subnet mask to the interface requesting an IP address.

2. DHCP option 3: Acquire IP through the interface's default router or feedback gateway.

3. DHCP Option 6 is also called DNS server which is used to assign the DHCP client a DNS server. 

4. DHCP Option 51 is also called the lease time option in which lease time for the DHCP client is assigned.

5. DHCP Option 42 is also termed anNTP server and is used to assign the NTP server to the DHCP client.

6. DHCP Options 69 and 70 are used for email transmission and receiving with SMTP and POP3 servers.

7. DHCP Option 81 enables automated updating of the client's related DNS entries.

8. DHCP Option 138 gives the DHCP client access to CAPWAP Access Controller addresses.

9. DHCP Option 150 gives the DHCP client access to a TFTP server.

Vendor class identification (a.k.a option 60) and client identifier (a.k.a option 61) are the two primary types in the DHCP option list when it comes to client requirements. The MAC address of the network interface on a local network is typically used as the client identification since it is distinct and aids the DHCP server in managing its clients and leases. The vendor class identification, which describes the vendor type and settings of a DHCP client in a short character string, is more intriguing. The format is flexible and open, allowing the server to modify the content and answer options as needed.