DNS Flush

Peter Parker

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I got home yesterday an discovered that while my laptop could log on to various networks it did not have internet access. This was true by WiFi or ethernet, All other devices were fine. I rebooted the laptop the router and the modem. I even connected the laptop directly to the modem. Still nothing.

I finally used my phone and one of the many suggestions I found was to do a DNS Flush. That worked but I am curious as to what may have caused this and why a DNS Flush worked. Any thoughts?
 

harshness

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You likely stumbled across something that filled your DNS cache with garbage. The industry (and Google search) term is "DNS cache poisoning".

I recommend that you update and run Malwarebytes to see if you have some sort of malware that is injecting the poison into your system. DNS poisoning can also come from nefarious web scripts.
 
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Peter Parker

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I tried MalwareBytes, Simple Malware Protector, and one other. Nothing found.
 

harshness

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If there's nothing resident, it probably came from a web-based script (or, and much less likely, Malwarebytes doesn't know about it yet).

Just to be safe, you might want to confirm that there aren't any alternate DNS servers set up. You can check this by running "ipconfig /all" at a command line and visually scan for the "DNS servers" information under your primary network adapter. Typically you should see only your router's IP address.
 
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navychop

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Absolutely check the DNS server. You do know you can specify alternates from what your ISP uses?

Not so sure about router IP for DNS server. I can easily specify who I want externally. Tried it years ago. With FiOS I just go with the flow.
 
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Foxbat

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You could override your defaults to test by setting Google's DNS servers 8.8.8.8 and/or 8.8.4.4 and see if that speeds things up. If you never changed the default password on your router it is feasible that some third party could have hijacked your DNS, or like harshness suggests, it could simply be DNS poisoning your local cache which slows you down.
 

harshness

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Not so sure about router IP for DNS server.
This is the default DHCP behavior on most all consumer routers as well as the third party firmwares and *nix-based firewall distributions (pfSense, ClearOS, IPCop, Untangle).

My point was that if your computer shows something other than the router's ip address for its DNS (obtained via DHCP), you had better know why.
 

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