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Building a DNS Server

The Domain Name System (DNS) is the phonebook of the Internet. Setting up your own DNS server gives you control over local network resolution and caching.

Concepts​

  • BIND9: The most widely used DNS software on the Internet.
  • Zone Files: Text files that contain mappings between domain names and IP addresses.
  • Forwarding: Sending unresolved DNS queries to external servers like Google (8.8.8.8) or Cloudflare (1.1.1.1).

Step-by-step Guide​

1. Install BIND9​

sudo apt update
sudo apt install bind9 bind9utils bind9-doc -y

2. Configure Local Caching DNS​

Edit /etc/bind/named.conf.options:

acl "trusted" [
    127.0.0.0/8;
    192.168.1.0/24;
];

options [
    directory "/var/cache/bind";
    recursion yes;
    allow-query [ trusted; ];
    forwarders [
        1.1.1.1;
        8.8.8.8;
    ];
    dnssec-validation auto;
    listen-on-v6 [ any; ];
];

3. Restart BIND9​

sudo systemctl restart bind9
sudo systemctl enable bind9

Best Practices​

  • ACLs (Access Control Lists): Only allow trusted IPs to query your DNS server to prevent DNS amplification attacks.
  • DNSSEC: Enable DNSSEC to protect against DNS spoofing.
  • Redundancy: Always set up a secondary (slave) DNS server for high availability.