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In this piece, we’ll talk about how to Diagnose DNS problems. The DNS (domain name system) is a database that saves information about domain names. The client-server tool turns domain names into IP addresses and IP addresses into domain names. DNS is also used by most other network services, like the Web, email, and file sharing.

Connectivity problems can be caused by a DNS service that is not set up correctly. It’s so easy, simple, and straight-forward to surf the web that it almost feels like a reflex. Sure, you know that this is made possible by a lot of simple technology, but who cares when it just works?

That doesn’t make it any less annoying, though, when you all of a sudden have trouble loading pages, find dead websites everywhere, or run into other web-based problems. If you can’t connect to the Internet on more than one website, it might seem like you’ll never be able to fix it yourself. However, this isn’t always the case; DNS (Domain Name System) problems are often to blame.

Ways to Diagnose DNS problems

Verify your DNS server IP addresses are correct and in order

Once you know you can connect to the network and have a valid IP address, let’s learn more about DNS by making sure your DNS Server IP addresses are correct and in the right sequence.

The IPv4 DNS Server IP numbers can be seen in Figure 2 above. Both of these are on our local LAN or subnet, so we can reach them even if my usual gateway isn’t working. On most business networks, this is how it works. But your DNS services don’t have to be on your subnet all the time. Most ISPs would not even have the DNS Server IPs on the same subnet as the default gateway.

Most home and small business routers don’t have their own DNS servers, so the SMB router acts as a proxy to connect DNS requests to the real DNS servers. In that case, your DNS Server IP address may be the same as your router’s.

Check for network connectivity

DNS is often the wrong thing to blame if you start your web browser, go to a URL, and the URL doesn’t bring up a website. In fact, your network connection is much more likely to be the problem.

This is especially true if you have a laptop that uses Wi-Fi networking. With wireless security methods, the key will be renegotiated every so often or the signal strength will weaken, which will cause the connection to the network to be lost. Any type of network makes it possible to lose connection.

In other words, before you blame DNS for your problems, check “OSI Layer 1 – Physical” and then make sure your network is connected. Here, you should be able to find a wireless Internet link that works. Take note of how Access is both local and online. If it just said “Local,” you don’t have a real network address. (you only have a private APIPA that starts with 169.x.x.x).

Now I can talk about my next point. Make sure that your network has a correct IP address. If you go to View Status on the screen above and then to Details, you can check your IP address and confirm the IP numbers of your DNS servers. Again, you can’t get to the Internet if your IP address is 169.x.x.x.

Check the DNS Server and restart services or reboot if necessary

Obviously, you won’t be able to fix it on the client side if the DNS server is really stuck, down, or set up wrong. You might be able to find a way around the down service, but you won’t be able to fix it.

So, it’s possible that you or the person in charge of the DNS server will need to check the status and settings of the DNS server to fix your DNS problem.

Check your DNS suffix

If you look up a local host on a DNS server that your PC is part of, you might be talking to a host without using the FQDN (fully qualified DNS name) and instead relying on the DNS suffix. If we wanted to connect to “server1,” for example, the DNS server might have more than one entry for that DNS name.

You should set up your network adapter with the connection-specific DNS suffix, as shown on the first line of the image above, called Figure 1. Notice how our DNS suffix, wiredbraincoffee.com, is shown at the end of that image. When we put just a DNS name, like server1, the DNS suffix is added to make it server1.wiredbraincoffee.com.

Ping the IP address of the host you are trying to get to

Pinging the IP address of the host you are trying to reach is a quick way to show that it is a DNS problem and not a network problem. If the connection to the IP address works but the connection to the DNS name fails, you know that the problem is with DNS.

We know that if your DNS Server isn’t working, it might be hard to figure out what the IP address is that you want to connect to. So, you would need a network diagram or, like many network administrators, just the IP address of a shared host to run this test. If this works, you could map the IP to the address by adding a line to your hosts file until the DNS server is back online.

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How to Diagnose DNS problems