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I have this mini router and on today I get slow internet speed with it on my desktop which has ubuntu. I have connected my laptop with the router and I got faster internet on the laptop. So I turned on the tethering on my phone and connected my desktop and now my internet connection is fast. However, when I connected with my router the internet is extremely slow on my desktop. I don't know what causes the problem.

I have this problem after I used a Mozilla extension named firex proxy.

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  • There are at least two possible different problems; 1) bandwidth (try any speed test site), 2) DNS resolution that points to an unreachable server (used a VPN recently)? You can at least check #1 and update your question with the results.
    – xenoid
    Apr 8, 2019 at 12:30
  • @xenoid Yes, you are correct I have used the VPN recently to get into a torrent site. It was a Mozilla extension named firex proxy. How do I get my previous speed?
    – Phil
    Apr 8, 2019 at 13:05
  • What I suspect is that your DNS is pointing to the VPN; so check /etc/resolv.conf, normally in Ubuntu (16+ at least) your DNS is 127.0.1.1, (Ubuntu uses dnsmasq) if you have anything not in 127.0.x.x you can remove it.
    – xenoid
    Apr 8, 2019 at 15:23
  • @xenoid I have nameserver 127.0.0.53 options edns0 in the resolv.conf. So do I need to remove it?
    – Phil
    Apr 8, 2019 at 15:55
  • Maybe. Do you recognize that edns0 string? Name of some interface? Is that you Ethernet or was that the tunnel? Replace by plain nameserver 127.0.1.1 and see if it fixes/breaks things and restore if breaks.
    – xenoid
    Apr 8, 2019 at 16:14

1 Answer 1

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Slow internet can be due to name resolution problems. Some VPN setups change the DNS resolution to point to the VPN name servers, and it is not always correctly restored when the VPN is shut down. Afterwards your name resolution is slowed down because it tries to query a name server that has become unreachable.

You can fix this by editing /etc/resolv.conf and remove foreign references. In modern Ubuntu (at least since 16.04) DNS is managed by resolvconf/dnsmasq and this requires your system to be its own name server (it will query other name servers under the hood). So in practice your /etc/resolv.conf will/should always looks like this when you are only connected to regular interfaces:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 127.0.1.1

If you find other DNS in it you can try to remove them.

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