Setup DNS Caching Server in Rocky Linux 8

Introduction

DNS caching improves the performance of domain name resolution by storing previously queried results locally.
A caching DNS server reduces the load on upstream DNS servers and speeds up repeated queries.
In this guide, we will configure a caching DNS server on Rocky Linux 8 and cover troubleshooting and security best practices.

Benefits of DNS Caching Server

• Faster DNS resolution for frequently accessed domains.
• Reduces network traffic to external DNS servers.
• Improves reliability during upstream DNS downtime.
• Helps in DNS load balancing for enterprise networks.

Step 1: Install Bind (DNS Server)

sudo dnf install bind bind-utils -y

Step 2: Configure Caching in BIND

Edit the main configuration file:

sudo vi /etc/named.conf

Make sure you have the following options for caching:

options {
    listen-on port 53 { any; };
    listen-on-v6 { any; };
    directory       "/var/named";
    dump-file       "/var/named/data/cache_dump.db";
    statistics-file "/var/named/data/named_stats.txt";
    memstatistics-file "/var/named/data/named_mem_stats.txt";
    allow-query     { any; };
    recursion yes;   // Enable caching
    forwarders { 8.8.8.8; 8.8.4.4; };  // Upstream DNS servers
};

Step 3: Start and Enable DNS Service

sudo systemctl enable --now named
sudo systemctl status named

Step 4: Adjust Firewall

sudo firewall-cmd --permanent --add-service=dns
sudo firewall-cmd --reload

Step 5: Verify Caching

Use dig to test DNS caching:

dig @localhost example.com

Check the SERVER: field and response time to verify caching works.

DNS Troubleshooting

• Check service status: systemctl status named
• Test DNS resolution: dig @localhost domain.com
• Check logs for errors: journalctl -u named or /var/log/messages
• Verify port 53 is open: ss -tulpn | grep 53

DNS Security Best Practices

• Allow queries only from trusted networks using allow-query.
• Disable recursion for public servers if not needed.
• Use forwarders carefully to trusted upstream servers.
• Regularly update BIND to patch security vulnerabilities.
• Enable logging and monitor for suspicious activity.

Server Information

Package Name: bind
Configuration File: /etc/named.conf
Service Name: named
Port: 53 (UDP/TCP)
Server IP: Example - 192.168.1.100

Conclusion

By setting up a caching DNS server, administrators can reduce latency, improve reliability, and enforce DNS security policies.
Regular monitoring and proper configuration ensure efficient and safe DNS operations in enterprise environments.