Today, I load up Ubuntu as normal, but although my web browser will display my router's "admin page" (like it normally would) where I can see total amount downloaded etc, it refuses to browse to any other page on the internet. Evolution does not want to get my emails either. However, Transmission is okay downloading and uploading files/torrents. Router seems logged onto internet okay, so clearly I'm connected to something.

Neither Firefox nor Chrome will bring up any web content.

However, my system is dual-boot so on loading into Windows XP to see what happens, browsing is normal, no problems. In fact I am typing this message from Windows - no choice!

I remember something about a "DNS cache" being corrupted as being the reason for browsing not being possible sometimes; however one website says "Ubuntu doesn't cache DNS records by default so unless you've installed a dns cache there isn't anything to clear".

So, given my inability to surf in Ubuntu, or retrieve emails, but my Transmission working fine, can anyone guess what is wrong with my Ubuntu system? Should I flush the DNS cache, and if so, how?

Thank you for any advice you can give.

Can you ping/browse an ip address rather than domain name?
ie:
and then try browsing to the same?

Can you:
On the windows machine, find out the DNS server (Network interface, properties somewhere (im rusty when it comes to windows).
Compare that to the contents of /etc/resolv.conf.

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Ah. I went back into Linux and typed those commands in, and now the browsing is working again. Thank you very much for that. However, I have discovered that starting Transmission stops the browsing working again, and in order to get it going I have to come out of Transmission and Firefox, run your Ping command again, then go back into Firefox and its working again.

What's going on, any idea? This has never happened before, is Transmission doing something bad?

I am going to take a wild guess that transmission is chewing all your bandwidth... or at least your uplink.
This will make it difficult for you to send packets out (to webservers/email/anything).

Check the current bandwidth usage with transmission, ill bet either the upload or download is maxing out your connection.

Nope, it's not that. I checked I was able to browse okay, then started Transmission. It was uploading 10Kb/s and not downloading anything, and I was then unable to surf to any new sites. Had to do the Ping command again (and close down Firefox and Transmission) to permit surfing again.

My router is reported Downstream of 6,680 Kbps and upstream of 888 Kbps.

Any further ideas? Otherwise I will just have to use Transmission when I am not browsing, and vice versa!

I don't think the ping is related. I only suggested that as a diagnostic, to test if it was a connectivity problem or a DNS problem.

Can you try with a different torrent client. To isolate if it is a tranmission problem, or a torrent protocol problem.

(I havent used transmission for a long time, so im not sure what could be causing the problem)

Moved: This thread is more suitable in <Linux-Networking> and has been moved accordingly to help your thread/question get the exposure it deserves.

Sigh... 24 hours later and now everything is working okay again. But thank you for your assistance, fukawi1.