Understanding Trailing Dots in DNS Records & Troubleshooting "DNS_PROBE_FINISHED_NXDOMAIN" Make it Rain Paper

Pre-requisites:

• Basic understanding of DNS and how it operates.
• Access to a DNS management interface, such as cPanel.

This article provides guidance on when to specify a trailing dot when adding a DNS record and troubleshooting common DNS resolution errors.

What is a Trailing Dot in DNS Records?

A trailing dot (.) at the end of a DNS record signifies that the name is fully qualified. This period indicates the root of the DNS hierarchy. Without the trailing dot, the DNS server assumes the record is relative to the current zone and may append the domain name automatically.

When to Use a Trailing Dot

When adding a DNS record, always include the trailing period after the domain name. For example:

example.com.

If the trailing dot is omitted, the DNS server will append your domain name to the record, which may lead to incorrect resolutions.

Troubleshooting "DNS_PROBE_FINISHED_NXDOMAIN" Error

The "DNS_PROBE_FINISHED_NXDOMAIN" error indicates that the browser cannot resolve the domain name to an IP address. This can often be traced back to configuration issues with your nameserver.

PowerDNS Configuration

As of cPanel version 84, PowerDNS is the default nameserver. In earlier versions, BIND was used. If PowerDNS is not configured correctly, it may lead to DNS resolution errors.

Identifying Configuration Issues

Check the installation log for PowerDNS at:

/var/log/cpanel-install.log

You may see a message indicating that PowerDNS was not configured correctly:

PowerDNS does not act as a recursive (caching) nameserver and your resolv.conf file references a local IP address.

Resolving DNS Issues

1. Check Remote Nameservers: Ensure that your /etc/resolv.conf file includes reliable remote nameservers, such as:

nameserver 8.8.8.8
nameserver 8.8.4.4

1. Force Reinstall PowerDNS: If the nameservers are correctly set, forcefully reinstall PowerDNS with the following command:

/scripts/setupnameserver --force powerdns

Once these steps are completed, PowerDNS should be configured correctly and ready to serve DNS requests.

Using a trailing dot in DNS records is crucial for accurate domain resolution, and understanding how to troubleshoot common DNS errors like "DNS_PROBE_FINISHED_NXDOMAIN" can help maintain the accessibility of your services. By following the steps outlined in this article, you can ensure proper DNS configuration and resolve common issues effectively.