Configuring DHCP with Dnsmasq 🌐

Dnsmasq is a versatile tool that provides DNS, DHCP, TFTP, and PXE services. Here, we focus on using Dnsmasq as a DHCP server. Here's a summary of the key points:

Overview of DHCP Configuration

1. DHCP Server Basics

   • A DHCP server assigns IP addresses to devices on a network.

   • It operates on a machine or device with a static IP address and is connected to the network it serves.

   • In practice, DHCP servers and clients usually run on separate machines, but for simulation, we use a single machine.

2. Interface Configuration

   • DHCP Server Interface (eth_srv): This interface will serve DHCP requests. Example IP: 192.168.1.1 with a subnet mask /24.

   • DHCP Client Interface (eth_cli): This interface will request an IP address from the DHCP server. Initially, it has no IP configured.

3. Basic DHCP Configuration with Dnsmasq

   • Create a configuration file (dhcp.config) with the following options:

     • interface: Specifies which interface Dnsmasq listens to for DHCP requests.

     • bind-interfaces: Ensures Dnsmasq only listens on the specified interface.

     • domain: Provides the network domain name to clients.

     • dhcp-option: Configures additional information for clients (e.g., default gateway, DNS servers).

     • dhcp-range: Defines the range of IP addresses available for lease, and the lease duration (e.g., 12 hours).

4. Starting Dnsmasq

   • Run Dnsmasq with the command:

     sudo dnsmasq -d -q -C dhcp.config

   • This command starts Dnsmasq with debugging information and the specified configuration file.

5. Testing DHCP Functionality

   • Use a DHCP client (dhclient) to request an IP address from eth_cli:

     sudo dhclient -i eth_cli -v

   • This command shows the exchange of packets and acquisition of an IP address (e.g., 192.168.1.80).

6. Verification and Results

   • After acquiring an IP address, use dig to query the DNS server:

     dig @localhost instance-1

   • Dnsmasq not only assigns IP addresses but also provides DNS services, resolving local queries based on its configuration.

7. Best Practices

   • Perform simulations and tests on a separate network from production to avoid disruptions.

Summary

• Dnsmasq is a lightweight solution that can serve both DNS and DHCP functions effectively.

• Configuration involves setting up interfaces, configuring DHCP options, and starting Dnsmasq with appropriate settings.

• Testing with dhclient and dig ensures that Dnsmasq is functioning correctly.

This setup demonstrates the dual role of Dnsmasq in managing both DNS and DHCP services, offering a compact yet powerful solution for network management. 🚀🔧