DHCP and DNS: Definition and purpose
When you connect to the internet, two behind-the-scenes technologies help make the experience fast and effortless. One makes sure you don’t have to remember complicated IP addresses to visit websites, and the other automatically gives your device the settings it needs to get online. These are DNS and DHCP.
What is DHCP?
Dynamic Host configuration Protocol, or DHCP, is a network protocol that assigns a device its IP address and related IP information. DHCP is an efficient way to distribute available addresses. It automates the process and network settings, making it efficient and resource saving. This protocol helps reduce manual configuration errors and simplifies managing devices on large networks.
What is DNS?
The Domain Name System (DNS) is an internet service that translates human-readable domain names into IP addresses. For example, when you type "www.google.com," the DNS system uses DNS servers to convert that domain name into an IP address. These DNS servers work behind the scenes to make it possible for you to access websites without needing to remember the complex IP addresses associated with them.
DHCP vs. DNS: Key differences
DHCP and DNS each have a unique role in network connectivity. Let’s take a look at the main differences:
Ports
Each protocol communicates over specific network ports. DNS uses port 53 for both TCP and UDP traffic, handling domain name queries and responses. DHCP, on the other hand, uses UDP ports 67 (for the server) and 68 (for the client), which are used during the IP address assignment and renewal process.
Server
The DHCP server automatically assigns IP addresses and other network configuration details to devices for a specific lease period. These settings can be renewed or reallocated as needed.
The DNS server receives domain name queries from client devices and responds with the corresponding IP address, helping devices find websites and services.
Type of system
DHCP is a centralized system, meaning one or more dedicated DHCP servers manage and distribute IP address information across the network. This function makes administration easier and ensures consistent address management.
The DNS is decentralized and relies on a distributed network of servers worldwide. Each server holds a portion of the global domain name database and works together to resolve names quickly and reliably.
Features
DHCP allots IP addresses for specific lease times and provides extra information, such as the host's IP address and the computer's subnet mask.
The DNS translates names into IP addresses and does the same in reverse. It can also be used for finding active directory domain servers.
Security
The DNS generally requires security extensions, such as DNS Security Extensions (DNSSEC). DNSSEC is used to protect against attacks and can work with other security measures like Secure Sockets Layer (SSL) and Transport Layer Security (TLS).
DHCP systems adopt layered security to protect them from threats. Firewalls filter traffic, data encryption reduces data breaches, authentication and access control allow for authorized access, and logging monitors suspicious behaviors.
DHCP vs. DNS comparison table
The table below compares DHCP and the DNS:
| Category | DHCP | DNS |
|---|---|---|
| Ports | Uses UDP port 67 (server) and UDP port 68 (client) for assigning and renewing IP addresses. | Uses port 53 (TCP and UDP) to handle domain name queries and responses. |
| Server | Automatically assigns IP addresses and network configuration details to devices for a limited lease period. | Resolves domain name queries by returning the associated IP address to client devices. |
| Type of system | Centralized. One or more DHCP servers manage IP address distribution across the network. | Decentralized. A distributed network of servers worldwide share the domain name database. |
| Features | Assigns IP addresses, subnet masks, and other config info. Lease times can be renewed. | Translates domain names to IP addresses (and vice versa), and can locate services like Active Directory domain servers. |
| Security | Uses layered security, such as firewalls, encryption, authentication, access control, and logging, to mitigate threats. | Uses DNSSEC to protect integrity and authenticity. It can be paired with SSL/TLS for enhanced security. |
How do DHCP and DNS work?
DHCP and the DNS both play crucial roles in network communication, but they work in very different ways. While DHCP helps devices get the necessary IP addresses to join a network, the DNS helps translate human-friendly domain names into the IP addresses needed to access websites.
How does DHCP work?
DHCP operates by leasing IP addresses and information to network clients for predetermined periods of time. DHCP clients start by broadcasting a discovery to find a server. The server responds by offering an available IP address. The client then formally requests that IP, and the server completes the process by sending an acknowledgment to confirm the lease.
Here’s how a dynamic IP address that gets assigned from the DHCP server:
- 1.DHCP discovery occurs when the client computer submits a packet with its name and MAC address to find a DHCP server.
- 2.A DHCP offer occurs when the server answers to “discovery” with an offer of an available IP address.
- 3.The DHCP request happens when the client computer responds with a request to ask the DHCP server for the available IP address.
- 4.After assigning an IP address, the DHCP server sends a DHCP acknowledgment (ACK) message, confirming the lease and informing the client that it can use the assigned IP address.
In other words, it’s a quick back-and-forth conversation between a DHCP client (X) and a DHCP server (Y):
X: Who can send my device an IP address?
Y: I’ll look. This one is available.
X: Thanks, I’ll take it.
Y: You’re welcome. Here it is.
How does the DNS work?
The DNS works by translating domain names that people can easily remember into IP addresses used by computers. When individuals type in a domain name such as nordvpn.com, the internet browser doesn’t know how to find the site. DNS sends a query to the LDNS (local DNS server) and asks questions like “What’s the IP address of nordvpn.com?” If the LDNS doesn’t contain records for nordvpn.com, it searches the internet to find its owner.
Here’s how it works:
- 1.A device sends a query to the LDNS, which sends it to a root server and directs it to the .com DNS server.
- 2.The .com DNS server responds to the LDNS by providing a referral to the authoritative name server responsible for the domain, including its name server records.
- 3.The LDNS requests an address record, including the site's IP address.
- 4.After getting the address record, the LDNS sends the IP address to the browser and stores the IP address information for the future.
How do DHCP and the DNS work together?
While DHCP and the DNS serve different purposes, they work together to enable seamless internet connectivity. DHCP assigns IP addresses to devices on a network, ensuring they can communicate with one another. Once a device has its IP address, the DNS comes into play, translating human-readable domain names like “google.com” into the IP addresses that computers need to locate those websites. Together, they help users easily access websites and browse the internet without needing to manage complex network settings manually.
