Using Domain Lookup for DNS Troubleshooting

A staging environment is down, you can't connect to the API, or the site opens for some users but not at all for others. In such cases, the problem is usually on the DNS side; however, for many developers, DNS still looks like a bit of a "magic" box.

In this article, we will approach DNS from a practical perspective and show you how to diagnose real issues using the Domain Lookup tool on JrDevTools.

1. A Quick Look at DNS Fundamentals

DNS (Domain Name System) is the system that translates human-readable domain names (e.g., jrdevtools.com) into IP addresses. The record types you will encounter most frequently are:

• A record – Points a domain to an IPv4 address.
• AAAA record – Points to an IPv6 address.
• CNAME – Creates an alias for another domain name.
• MX – Defines email servers.
• TXT – Used for verification and various textual information.

The Domain Lookup tool makes it easy to read and visualize these records.

2. Why Does a Domain Work Differently for Different Users?

DNS records update at different times in different parts of the world due to TTL (Time To Live) values. Therefore:

• Even if you have pointed to a new IP,
• Some users may still see records leading to the old IP.

When you query a domain with Domain Lookup, by comparing responses from different DNS providers, you can see whether the changes have truly propagated.

3. Detecting Misconfigurations

If you constantly receive ECONNREFUSED, ENOTFOUND, or timeout errors when making a request to a service, follow these steps:

1. Copy the domain from the target URL (e.g., api.staging.example.com).
2. Paste it into the Domain Lookup tool.
3. Examine the A, AAAA, and CNAME records.

Common problematic situations include:

• The domain points to the wrong IP.
• The CNAME chain is incorrect or creates an infinite loop.
• IPv6 records are missing or incorrect, causing errors for clients trying to connect via IPv6.

These checks allow you to very quickly find the answer to the question "Is the server broken, or is it DNS?".

4. Ensuring Consistency Across Environments

If you have development, staging, and production environments, the consistency of DNS configurations is critically important. For example:

• api.dev.example.com
• api.staging.example.com
• api.example.com

By querying each of these domains with Domain Lookup, you can regularly review:

• Which IPs they point to,
• Whether they go to load balancers or reverse proxies in the same region,
• Whether there are unnecessary or obsolete records.

5. The Relationship Between SSL and DNS

Although most SSL/TLS errors do not stem directly from DNS, a DNS record pointing to the wrong domain can lead to certificate errors. For example:

• If the certificate was issued for api.example.com, but requests are accidentally going to the IP of old-api.example.com.

In such cases, first ensure you are really going to the correct IP with Domain Lookup, then check the certificate configuration. When these two layers are handled together, the cause of many "mysterious" SSL errors becomes clear.

6. Conclusion: Making DNS Less of a Black Box

You don't need to read all the RFCs to start understanding DNS. With a few simple tools and routines in your daily workflow, you can solve most problems in minutes. The Domain Lookup tool on JrDevTools is designed to streamline this process with a specifically developer-focused interface.

The next time you hear that an environment is broken "only for some people," open this tool first and check the DNS records. Often, the problem stems from a simple DNS inaccuracy rather than a complex application error.

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