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I have Fedora 11 in a Virtual Box VM and because of a bad DNS configuration my network connection in that VM was awfully slow.

I fixed it now, but I don't understand what happened and I'm curious about what was going on.

I set a primary and a secondary DNS server. The primary server was misconfigured and most of the times did not respond. The secondary was fine.

Normally I would expect slowdowns during the first time a connection is made to a host, when the host name is resolved.

Although that was always the case, additionally my overall throughput was very slow, i.e. when I was downloading a larger file from the internet. (5-20 KB/s as opposed to 1.5 MB/s) Sometimes the transfer spiked at 100-200 KB for a few seconds, sometimes there was no transfer at all for about 20-60 seconds. That was the case with all applications, Firefox and yum I thoroughly tested.

After removing the bad DNS server everything went normal again.

Could all this come from a bad DNS server? Or is this a Fedora or Virtual Box problem?

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up vote 4 down vote accepted

If you have bad DNS the initial request will be slow, then once the lookup is cached, your speed should be fine.

It may be a routing issue though with packets trying a wrong default gateway, I had that problem with my dual airport express' once I unplugged the one that was not connected to the net it was fine.

Start by doing a ping and a tracerouce and look at the latency and any dropped packets.

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