Building Your Local Network with DNSmasq and DHCP on AlmaLinux 9

In this guide, we’ll set up Dnsmasq to act as a DNS server and DHCP server to simplify local network management.

By İbrahim Korucuoğlu ( @siberoloji) | Thursday, November 28, 2024

Introduction

Managing local networks can be challenging without proper tools. Enter Dnsmasq, a lightweight and versatile solution for providing DNS and DHCP services on a single server. By leveraging Dnsmasq on AlmaLinux 9, you can efficiently configure and manage your network for both name resolution and dynamic IP allocation.

In this guide, we’ll set up Dnsmasq to act as a DNS server and DHCP server to simplify local network management.

Part 1: Installing and Configuring Dnsmasq

Dnsmasq is a streamlined tool that combines DNS caching and DHCP management, making it ideal for small-to-medium networks.

Step 1: Install Dnsmasq

Install the package:
```
sudo dnf install -y dnsmasq
```
Enable and start the service:
```
sudo systemctl enable dnsmasq --now
```
Verify the installation:
```
systemctl status dnsmasq
```

Step 2: Configure Dnsmasq

Dnsmasq’s configuration file is located at /etc/dnsmasq.conf. Here’s how to customize it for your network:

Edit the configuration file:
```
sudo nano /etc/dnsmasq.conf
```
Add or update the following settings:
- Enable DNS caching:
```
cache-size=1000
```
- Specify a local DNS domain:
```
domain=localdomain
```
- Set the DHCP range and lease time:
```
dhcp-range=192.168.1.50,192.168.1.100,12h
```
- Assign static IPs using MAC addresses (optional):
```
dhcp-host=00:11:22:33:44:55,192.168.1.10
```
Save and close the file, then restart Dnsmasq:
```
sudo systemctl restart dnsmasq
```

Step 3: Test Dnsmasq Configuration

Verify DNS functionality:
- Query a domain:
```
dig example.com
```
- Check cached responses:
```
dig example.com
```
Verify DHCP functionality:
- On a client, release and renew the IP address:
```
sudo dhclient -r && sudo dhclient
```
Check assigned IPs:
- View leases on the server:
```
cat /var/lib/misc/dnsmasq.leases
```

Part 2: Advanced Configuration for DNS and DHCP

Dnsmasq supports additional features to enhance your local network.

Step 1: Configure Custom Hostnames

Edit the /etc/hosts file:
```
sudo nano /etc/hosts
```

Add custom hostname mappings:

192.168.1.10 server1.localdomain server1
192.168.1.11 server2.localdomain server2

Restart Dnsmasq:
```
sudo systemctl restart dnsmasq
```

Step 2: Integrate with External DNS Servers

Edit /etc/dnsmasq.conf to specify upstream DNS servers:
```
server=8.8.8.8
server=8.8.4.4
```
Clear the DNS cache:
```
sudo systemctl restart dnsmasq
```

Step 3: Troubleshooting Dnsmasq

Check logs for issues:
```
sudo journalctl -u dnsmasq
```
Test configuration syntax:
```
sudo dnsmasq --test
```
Ensure no port conflicts:
- Stop conflicting services:
```
sudo systemctl stop systemd-resolved
```

Part 3: Secure and Optimize Dnsmasq

Step 1: Restrict DNS Queries

Limit queries to internal clients:
- Add the following to /etc/dnsmasq.conf:
```
interface=eth0
bind-interfaces
```
Restart Dnsmasq:
```
sudo systemctl restart dnsmasq
```

Step 2: Enable Logging

Enable detailed logging for troubleshooting:
- Add to /etc/dnsmasq.conf:
```
log-queries
log-facility=/var/log/dnsmasq.log
```
View logs:
```
tail -f /var/log/dnsmasq.log
```

Step 3: Optimize for Performance

Increase cache size:
- Update /etc/dnsmasq.conf:
```
cache-size=2000
```
Enable asynchronous DNS processing:
- Add:
```
dns-forward-max=150
```

Conclusion

With Dnsmasq configured, you now have a lightweight and efficient solution for managing DNS and DHCP services on your AlmaLinux 9 server. This setup is perfect for small to medium networks, offering a robust way to handle name resolution and IP allocation.

What’s Next?

In the next post, we’ll delve deeper into configuring a full-fledged DNS server using BIND to manage internal and external domains with greater control.

Last modified 09.01.2025: msfconsoel translations ongoing... (f7e18da)