DHCP Port Number: Well-known Ports for Client and Server

DHCP (Dynamic Host Configuration Protocol) is a network protocol used to automatically assign IP addresses and network configuration information to devices on a network. It follows client-server architecture. When a client device connects to a network, it can request an IP address from a DHCP server, which will lease an available IP addresses for a specific period. This makes it easier to manage and configure IP addresses for multiple client devices on a network. The well-known port numbers used by DHCP server and client are 67 and 68 respectively.

What is port number ?

The end point of a logical connection is known as port. Port number is logical address of each application or process or program which uses network or internet connection in order to communicate. In TCP/IP network, it helps sender and receiver to communicate with each other. Port number is 16 bit in size which takes any value from 0 to 65536. The port numbers from 0 to 1024 are known as well known ports and are used for specialized services or privileged services.

IP address and port number are used to deliver data packets to its destination device. IP address resembles to apartment building or flat building housing multiple flats/apartments. The port number resembles to individual apartment or flat number. IP address/port number can be written as 192.168.1.68:8080 where in first four digits are IP address and last digit "8080" is port number.

What is DHCP Protocol ?

The default port number for DHCP server is 67 and the default port number for DHCP clients is 68

How DHCP works

• DHCP is defined in RFC 2131.
• It runs over UDP.
• It provides automatic configuration of host connected to the network or booted while connected on the network.
• It provides hosts with initial configuration data which includes IP address with subnet mask, default gateway and IP address of the DNS server
• The figure depicts how DHCP works. As shown DHCP client requests for its configuration from DHCP server. Upon receiving the request, DHCP server replies the information to the client. These include IP address, subnet mask, default routers, DNS servers, lease time etc.
• DHCP server dynamically assigns IP address on demand to the DHCP clients.
• DHCP uses UDP port number 67 as destination server and port number 68 for the client.
Refer DNS vs DHCP >> for difference between DHCP and DNS protocols.

Conclusion :

In summary, the DHCP protocol plays a crucial role in network management by automating the assignment of IP addresses and other network configurations to devices. The well-known port numbers associated with DHCP are 67 for the server and 68 for the client, facilitating the dynamic and seamless distribution of IP addresses. This protocol significantly reduces the administrative burden of managing IP addresses manually and ensures efficient IP address utilization within a network.

Understanding DHCP and its port numbers is essential for network administrators and IT professionals, as it underpins the functionality and scalability of modern network infrastructures. By mastering the details of DHCP, one can ensure robust and reliable network performance, enabling seamless connectivity for all networked devices.


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