Terminology » Networking Basics » DHCP Port Number: Client and Server Well-Known Ports

DHCP Port Number: Client and Server Well-Known Ports

dhcp port number network protocol ip address network management

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 a 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 address 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 a Port Number?

The endpoint of a logical connection is known as a port. A port number is a logical address of each application, process, or program which uses a network or internet connection in order to communicate.

In a TCP/IP network, it helps the sender and receiver to communicate with each other. A port number is 16 bits in size, which can take any value from 0 to 65536.

The port numbers from 0 to 1024 are known as well-known ports and are used for specialized or privileged services.

IP addresses and port numbers are used to deliver data packets to their destination device. An IP address is like an apartment building housing multiple flats/apartments. The port number is like the individual apartment or flat number.

An IP address/port number can be written as 192.168.1.68:8080, where the first four digits are the IP address and the last digit “8080” is the 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 hosts 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 the IP address of the DNS server.
  • The figure above depicts how DHCP works. As shown, a DHCP client requests for its configuration from a DHCP server. Upon receiving the request, the DHCP server replies with the information to the client. These include the IP address, subnet mask, default routers, DNS servers, lease time, etc.
  • DHCP servers dynamically assign IP addresses on demand to the DHCP clients.
  • DHCP uses UDP port number 67 as the destination server and port number 68 for the client.

Refer to DNS vs DHCP for the 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.