DNS trouble... what causes it ?

[Externet]

Greetings.

My compfuser stopped navigating the net by 00:00 GMT on 01 Oct.

8 of 10 web sites reported :

 

Few web sites did work and showed up normally.   Tried fixes shown on the web that claimed being a simple failure; two did nothing, a third fixed this DNS thing. Am back to 'normal'

I do not care what is the nature of the repair; I would like to know what causes such.  Was working normal and later, something changed.  And I did not do anything or tweaked or downloaded or changed settings.  What event caused it, came from where ?  Altered my equipment for what reason ?  How did it get into effect ?  Where did it come from ? 

On Firefox and on Chrome browsers, same behavior. 

[Am running Linux]

Running

[Endy0816]

Translation of the site's domain name to an IP address was having issues.

Think of it like mailing a letter.

Your computer knows the name of the person you are trying to reach, but needs to learn their address. That's what the Domain Name Server can provide.

 

Could well be the external server itself or at least reaching it causing the problem. There's a few possibilities though. What fixed it?

Edited October 2, 2021 by Endy0816

[Externet]

Thanks.  Understand the DNS 'directory'.    So the external server is the one troubling, not my comfuser...  Well, another computer at home running on the same house network did not fail its DNS. 🤨 

The image paragraph just before "2.-" below fixed it; but has a typographical error that I caught and corrected. "udo" for "sudo"

---> https://www.cloudns.net/blog/dns-probe-finished-nxdomain-explained/

I was scratching my head if the sharp time of DNS failure had something to do with the service provider...

 

[Endy0816]

Your computer can also save(or cache) a local copy of previously requested names and addresses, saving time. This can itself cause issues though.

 

[Sensei]

You can have Internet configured statically or dynamically (DHCP).

https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol

 

If it is static, you must enter the IP addresses manually.

 If it is dynamic, when establishing a connection, the computer asks the DHCP server (usually a router) for the local computer's IP address, gateway, IP mask, DNS servers, etc.

 

A dynamically configured Internet is less secure than a static one. If a hacker intercepts a router and changes the configuration of DNS servers in it, he/she will immediately find out what sites we visit. This is especially dangerous in free hot-spots of unknown origin (rented apartments, hotels, hostels, restaurants, shopping malls, streets, etc.).

 

To find out about DNS servers on a Windows machine, the user can open a terminal ("cmd" in Start), and type "ipconfig /all". This can also be done in the UI.

 

On Linux,

https://www.google.com/search?q=how+to+check+dns+linux

https://askubuntu.com/questions/191563/how-to-view-the-dns-address-assigned-by-dhcp

 

If the DNS servers provided by your ISP (via DHCP) do not work, try using Google DNS servers: 8.8.8.8 and 8.8.4.4

https://developers.google.com/speed/public-dns/docs/using

Google DNS servers are usually slower than ISP DNS servers, but their IP addresses are easy to remember, so just in case of local DNS problems (or hackers breaking in and intercepting your ISP DNS servers), it's good to know how to change your settings to static and use Google DNS servers instead.

 

The "nslookup" command in the terminal will tell you which DNS server was used to query the DNS entry. Either on Windows and on Linux.

e.g.

nslookup google.com ; it will use the default DNS configuration (perhaps DHCP, perhaps provided by the ISP)

nslookup google.com 8.8.8.8. ; it will use Google DNS servers instead of the default DNS.

so if you think hackers have hijacked your DNS server, you can verify this by comparing the results of these two commands.

(but some DNS records may be location dependent https://www.google.com/search?q=DNS+records+location+dependent )

 

18 hours ago, Externet said:

[Am running Linux]

Too ambiguous..

Edited October 2, 2021 by Sensei