DNS server randomly fails

Question

So everything was working correctly before, I had constant internet connection on my desktop computer.

Then I bought a laptop and connected it with WiFi to my network and I had internet on that too until recently.. my DNS server randomly fails on my desktop and can't resolve hostnames anymore, My internet connection is still working since I can still receive messages from Skype and such but I can't access anything that requires a DNS to resolve a hostname ( browsing the internet for example) .. sometimes this happens every 10 minutes and sometimes this doesn't happen for an hour and over. Everytime this happens I have to ipconfig /release and ipconfig /renew to get a new assigned IP, after I have done this the DNS just works again but it's getting quite annoying having to do this over and over.

I've already tried: 1. restarting my modem/router 2. flushing my DNS cache

Any idea on how to fix this or what is causing this?

Answer 1

First, I would recommend you try and determine where DNS is failing. It may be that it is local to your machine, or an issue at your router, or even that your ISP (this is assuming you rely on your ISP to provide DNS results).

So, when this happens, open up a command prompt and use nslookup to check your DNS.

Type 'nslookup' and you will go to an interactive prompt. By default, it will check A records, so type in something that you would expect to return such as 'google.com' and press enter. When it works, it will return the A records for google.com, so you should see the IP addresses for the domain. When it does not work, it will tell you it timed out, or that no record was returned.

Either way, it should first tell you the server that responded, this will let you know where it is trying to get its result.

So now you can use nslookup to change where you query. To do so you type in 'server IP-Address'. So for example, I often change to the following public DNS server to test 'server 4.2.2.2' (press enter to set). Then once again type in 'google.com' and press enter.

If this succeeds, then you know that it is the default DNS location that you normally query that is causing the issue. Here you have some options, you can usually change your router to point to the DNS server of your choice. It tends to default to your ISP... but maybe there is a better IP at your ISP to use, or you would like to use a public DNS, etc. Naturally you want to only use reputable DNS servers, as a compromised DNS server could provide you with altered records which would mean when you go to a site, you may actually be accessing a faked site (and providing login credentials to the wrong site for example).

You could also manually specify your own DNS server per computer (within the TCP/IP settings for your network connection).

The above is just the 'basic' most common explanation, there could be various other issues that can come to play. But start with using nslookup (on Windows machines, the tool 'dig' is the equivalent in Linux) to try and find the cause.

Answer 2

It's possible that the DNS server you're using is the modem/router. You can check for this by running ipconfig /all. Look for the Default Gateway IP address: this is the IP address of your modem/router. Then look for DNS Servers and se if it's the same address.

If the DNS server is in your modem/router then there are a couple of options. You can reconfigure your PC to use a specific DNS server by going to "Change Adapter Settings" and on the IP Version 4 Properties change from 'Obtain DNS Server address automatically' to 'Use the folowing DNS server addresses', and then enter the address(es) of the server(s) you want to use. Alternatively, you can update the modem/router settings to provide your preferred DNS server addresses through DHCP.

If you don't know what IP addresses to use for DNS servers, try 208.67.222.222 and 208.67.220.220 - these are servers run by OpenDNS.