Why does DHCP use TCP? (2023)

Does DHCP use TCP or UDP?

The DHCP employs a connectionless service model, using the User Datagram Protocol (UDP). It is implemented with two UDP port numbers for its operations which are the same as for the bootstrap protocol (BOOTP). UDP port number 67 is the port used by the server, and UDP port number 68 is used by the client.

DHCP runs at the application layer of the Transmission Control Protocol/IP (TCP/IP) stack to dynamically assign IP addresses to DHCP clients and to allocate TCP/IP configuration information to DHCP clients. This includes subnet mask information, default gateway IP addresses and domain name system (DNS) addresses.

DHCP includes the following features to reduce network administration: Centralized and automated TCP/IP configuration. The ability to define TCP/IP configurations from a central location.

TCP/IP defines how your PC communicates with other PCs. To make it easier to manage TCP/IP settings, we recommend using automated Dynamic Host Configuration Protocol (DHCP). DHCP automatically assigns Internet Protocol (IP) addresses to the computers on your network if your network supports it.

DHCP cannot use TCP as the transport protocol because TCP requires both end-points to have unique IP addresses. At the time a host is required to use DHCP, it does not have an IP address it can source the packets from, nor does it have the IP address of the DHCP server.

The reason TWO reserved ports are used, is to avoid 'waking up' and scheduling the BOOTP server daemons, when a bootreply must be broadcast to a client. Since the server and other hosts won't be listening on the 'BOOTP client' port, any such incoming broadcasts will be filtered out at the kernel level.

A TCP/IP host uses the DHCP (Dynamic Host Configuration Protocol) to obtain its configuration parameters (IP address, gateway, name servers, and so on) from a DHCP server that contains the configuration parameters of all the hosts on the network.

When a device wants access to a network that's using DHCP, it sends a request for an IP address that is picked up by a DHCP server. The server responds be delivering an IP address to the device, then monitors the use of the address and takes it back after a specified time or when the device shuts down.

Dynamic Host Configuration Protocol (DHCP) is a network protocol that is used to configure network devices to communicate on an IP network. A DHCP client uses the DHCP protocol to acquire configuration information, such as an IP address, a default route, and one or more DNS server addresses from a DHCP server.

Transmission Control Protocol (TCP)

What protocol and port does DHCP use?

DHCP uses UDP port 67 on the server side and UDP port 68 on the client side. DHCP also has two versions: DHCPv4 and DHCPv6 to support IPv4 and IPv6, respectively. These two versions, much like the two versions of IP, are very different and are therefore considered separate protocols and use separate ports.

DHCP is a network protocol to used to configure IP networks. A DHCP server listens to UDP port 67 and dynamically assigns IP addresses and other network parameters to DHCP clients. These clients will listen for responses on UDP port 68.

TCP stands for Transmission Control Protocol a communications standard that enables application programs and computing devices to exchange messages over a network. It is designed to send packets across the internet and ensure the successful delivery of data and messages over networks.

The main properties which we will be dealing with include Static IP Addressing, Dynamic IP Addressing, Reservations, Scopes, Leases and Options. It is interesting to know how most of the components of DHCP function collaboratively to make the system flawless.

TCP is a connection-oriented protocol, whereas UDP is a connectionless protocol. A key difference between TCP and UDP is speed, as TCP is comparatively slower than UDP. Overall, UDP is a much faster, simpler, and efficient protocol, however, retransmission of lost data packets is only possible with TCP.

DNS uses TCP for Zone transfer and UDP for name, and queries either regular (primary) or reverse. UDP can be used to exchange small information whereas TCP must be used to exchange information larger than 512 bytes.

HTTP and connections

Among the two most common transport protocols on the Internet, TCP is reliable and UDP isn't. HTTP therefore relies on the TCP standard, which is connection-based.

​ If the client receives several DHCPOFFER messages from different servers, it sends a unicast DHCPREQUEST message to the server from which it chooses to obtain the IP information.

The use of an well known port (in our case 68) prevents the use of the same two destination port numbers and hence it prohibits other protocols from using the same port which is already in use by another protocol. In simple words, it prevents an application from getting a message from a completely different protocol.

Is port 162 UDP or TCP?

TCP can be used for both 161/162, but UDP tends to be more common. Typically the agents are configured in read-only or read-write mode. The difference between the two is determined by the community string used. There are several versions of SNMP V1, V2c and V3.

TCP/IP specifies how data is exchanged over the internet by providing end-to-end communications that identify how it should be broken into packets, addressed, transmitted, routed and received at the destination.

TCP/IP is widely used primarily because it is standardized vs competing networking protocol suites such as IPX/SPX and Appletalk. The World Wide Web, the web, is another reason TCP/IP is so popular. HTTP is an application layer protocol designed within the framework of the Internet protocol suite.

TCP/IP stands for Transmission Control Protocol/Internet Protocol. TCP/IP is a set of standardized rules that allow computers to communicate on a network such as the internet.

DHCP runs over UDP over IP - it works the same whether wired or wireless. The DHCP client sends out a discover broadcast (which is bridged or optionally relayed by the WAP) and the DHCP server returns an offer. All you need is L2 connectivity which Wi-Fi and Ethernet provide alike.