Half Duplex ADSL Modem

Since my girlfriend and I are expecting another baby due around 20 November, Brecht will move from here current babyroom to the room that was used by me. So all my computers had to move as well. Last weekend we redid the wooden floor again (oiling), this weekend I moved my computers to the second floor. I rewired the PSNT/ADSL, moved my computers (closed the current case of Willt, this website since it had one harddisk outside), did the switches, the wireless etc. Then I booted and sure enought Linux was comming up fine. And even the ADSL worked, like a charm. Or so it seems.

The connection was very very slow. I open standard some 20 sites in firefox on my laptop and they loaded like when I had PSTN or even worse casema cable in the late 90ies. Showing Pat and mat videos to my doughter (buurman en buurman for the Dutch) from youtube, I found out that the loading took longer then the display time, not normal for the quality connection I have to XS4ALL. Doing some speedtest I saw that my download speed dropped from the normal 4Mb to 200Kb while my upstream capacity stayed at 600Mb (no torrents in the background).

And even worse, when I was doing a huge test download, the ADSL connection dropped after 10 seconds I had a link, so I had to shut the interface on my Linux box or my ADSL modem just to have 10 seconds of slow internet connection. Try to troubleshoot your connection without having a one!

Since I did some netmastering back in the 90-ies, I knew I was going to solve this one. The first thing I saw was that not the ADSL connection was dropping but the ethernet from my Linux box to my ADSL router. So it was local and should be easy to solve. Somehow, the link on my eth1 going to my modem was 10Mb full duplex auto negotiate. Now autonegotiate is bad and if you know the wirespeed on both sides, never use it!

So once I did a

ethtool -s eth1 speed 10 duplex half autoneg off
and the line was stable and fast again! I dont know how the wrong speed was changed. But I am sure glad to be online again. And I might have solved some other problems my website has as well. I'll keep you posted.