It can be a challenge to troubleshoot a null DNS lookup result for include. Fortunately, there are a few strategies you can use to resolve this issue.
Overview
A DNS lookup is a process used to match an IP address with its corresponding hostname. The DNS lookup process is needed to resolve an include file that is located by an absolute URL. This allows the web server to retrieve the necessary file.
When a null DNS lookup result occurs, it means the DNS server could not link the IP address to its corresponding hostname. This can prevent the requested file from being retrieved, resulting in an error or blank page.
In order to find and resolve the issue behind the null DNS lookup, you need to troubleshoot the request and its associated server environment.
Troubleshooting
The goal of troubleshooting DNS lookup issues is to identify why the server returned a null result instead of resolving the request.
In most cases, the problem is related to DNS misconfiguration, an invalid host entry, or an outdated DNS cache. Below, you will learn more about these issues and how to resolve them.
Check Your HOSTS File
Your HOSTS file contains a list of IP address and their hostnames. To check if there is an invalid or outdated entry, you need to open the file with a text editor.
- For Windows 10, go to C:\Windows\System32\drivers\etc\HOSTS.
- For MacOS X, go to /etc/HOSTS.
Once you open the file, you should be able to identify the hostname and IP address associated with the issue. If an entry is invalid or outdated, you can update it and save the file.
Flush Your DNS Cache
If the HOSTS file did not resolve the issue, you may have an out-of-date DNS cache. This can happen if the DNS data stored in your computer is outdated. To flush the cache, you will need to access your DNS settings.
- For Windows 10, click Start, type cmd into the search box, right-click Command Prompt, and select Run as Administrator.
- For MacOS X, go to System Preferences and select Network.
From here, you can run the commands specific to your operating system to clear the DNS cache and resolve the issue.
Clean Your Computer Registry
If you are still unable to resolve the issue, you may need to clean your computer registry. This can be done with a third-party cleaning tool. Before you run the cleaning tool, make sure to backup the original registry.
Once the registry is cleaned, you should be able to resolve the issue.
FAQ
What is DNS lookup?
A DNS lookup is a process used to match an IP address with its corresponding hostname. This allows the server to resolve the requested file and deliver it to the user.
What causes null DNS lookup results?
Null DNS lookup results can be caused by DNS misconfiguration, an invalid host entry, or an outdated DNS cache.
How can I check my HOSTS file?
You can go to C:\Windows\System32\drivers\etc\HOSTS (Windows 10) or /etc/HOSTS (MacOS X). This will open the HOSTS file in your default text editor.
How can I flush my DNS cache?
You will need to access your DNS settings. For Windows 10, click Start, type cmd into the search box, right-click Command Prompt, and select Run as Administrator. For MacOS X, go to System Preferences and select Network.
How can I clean my computer registry?
You can use a third-party cleaning tool. Before you run the tool, make sure to backup the original registry. Once the registry is cleaned, you should be able to resolve the issue.