How to Install and Setting DHCP Server DNSMasq on Ubuntu Server 24.10

Setting up a DHCP server is crucial for any network, especially when managing multiple devices. While manual configuration is possible, it's often tedious and prone to errors. Luckily, tools like Dnsmasq simplify this process, making it efficient and reliable.

This guide will walk you through installing and configuring a DHCP server using Dnsmasq on Ubuntu Server 24.10, empowering you to automate IP address assignment for your network.

Understanding the Fundamentals: DHCP and Dnsmasq

The Dynamic Host Configuration Protocol (DHCP) acts like a network traffic cop, automatically assigning IP addresses and other network configuration parameters to devices. It eliminates the need for manual configuration, making network management much smoother.

Dnsmasq, a lightweight DHCP server and DNS forwarder, is designed for both small and medium-sized networks. Its simplicity and flexibility make it an ideal choice for home networks, small offices, and testing environments.

Setting Up the Stage: Prerequisites and Configuration

Before we dive in, ensure you have the following:

• Ubuntu Server 24.10: This is the operating system we'll be working with.

• Root or sudo privileges: You'll need these permissions to install and configure Dnsmasq.

• Basic network administration knowledge: Familiarity with IP addressing, network masks, and gateways is helpful.

Step-by-Step Configuration

1. Installing Dnsmasq:

   • Begin by updating your package repository:

           sudo apt update
         

     
     

   • Install the Dnsmasq package:

           sudo apt install dnsmasq -y
         

     
     

2. Enabling and Starting the Service:

   • After installing Dnsmasq, you need to start and enable the service:

     sudo systemctl start dnsmasq
     sudo systemctl enable dnsmasq
         

     
     

   • To confirm that Dnsmasq is running, check its status:

           sudo systemctl status dnsmasq
         

     
     

3. Configuring the Dnsmasq Server:

   • Dnsmasq's configuration is primarily managed through the /etc/dnsmasq.conf file. You can also add user-defined configuration files to the /etc/dnsmasq.d directory.

   • Open the configuration file with your preferred text editor (we'll use nano here):

           sudo nano /etc/dnsmasq.conf
         

     
     

   • Now, let's add the following configuration options:

     dhcp-range=192.168.1.100,192.168.1.200,24h
     dhcp-option=option:router,192.168.1.1
     dhcp-option=option:dns-server,8.8.8.8
     dhcp-authoritative
         

     
     

   • Here's what these options mean:

     • dhcp-range: Specifies the range of IP addresses that the DHCP server will assign to clients. In this case, it's from 192.168.1.100 to 192.168.1.200, with a lease duration of 24 hours.

     • dhcp-option=option:router: Sets the default gateway for clients receiving IP addresses from this server. Here, the default gateway is set to 192.168.1.1.

     • dhcp-option=option:dns-server: Specifies the DNS server that clients will use to resolve domain names to IP addresses. This is set to Google's public DNS server at 8.8.8.8.

     • dhcp-authoritative: Designates this DHCP server as the authoritative source for DHCP information on the network. This ensures that if multiple DHCP servers exist, this server takes precedence.

   • Save the configuration file and restart the Dnsmasq service to apply the changes:

           sudo systemctl restart dnsmasq
         

     
     

   • Important Note: Adjust the values in the configuration options to match your network environment.

4. Firewall Configuration:

   • If you have a firewall enabled, you need to allow DHCP traffic:

     sudo ufw allow 67/udp
     sudo ufw reload
         

     
     

5. Configuring Clients:

   • Now, configure your client machines to obtain IP addresses automatically from the DHCP server.

   • Using Network Manager:

     • On most desktop environments, you can usually configure DHCP settings through Network Manager.

     • Open the Network Manager settings, select the network connection you want to configure, and choose "Automatic (DHCP)" as the IPv4 method.

   • Manual Configuration (CLI):

     • On a system like RHEL, use the nmtui tool:

             nmtui
           

       Navigate to "IPv4 Settings" and select "Automatic" as the method.

   • Verifying DHCP Assignment:

     • After configuring your client, verify that it has acquired an IP address from the DHCP server using the following commands:

       ip address show
       sudo dhclient -v
           

       
       

6. Inspecting Logs:

   • If you encounter any issues, examine the Dnsmasq logs:

           sudo journalctl -u dnsmasq
         

     
     

     • To search for specific events (e.g., related to a specific IP address), use grep:

             sudo journalctl -u dnsmasq | grep -i "192.168.1.102"
           

       
       

Conclusion

By following these steps, you have successfully set up a DHCP server using Dnsmasq on Ubuntu Server 24.10. You can now effortlessly manage IP addresses for your network, simplifying network administration and reducing configuration overhead.