Ethtool

Jerry Feldman gaf at blu.org
Wed Oct 22 13:48:22 EDT 2008


On 10/22/2008 10:31 AM, bruce.labitt at autoliv.com wrote:
> CentOS5.2, ethtool 5, Intel PCI 1000Mbit ethernet card - running e1000 
> driver.
>
> The connection from my pc to the local gbit switch is autonegotiating to 
> 10Mbit :(
> I tried using ethtool to change the connection speed and it seems either I 
> am not doing it right (most likely), or something is wrong.
>
> If I attach the NIC directly to my remote server it negotiates to 
> 1000Mbit, so I think the NIC is ok.  If I plug the remote server directly 
> to the switch, it negotiates to 1000Mbit, so I would think the switch is 
> ok. 
>
> So how does one set the speed in ethtool?
>
> # ethtool -s eth0 speed 1000 duplex full   ?
>
> How come this does not work?  Wrong syntax?  Something else?  I've tried a 
> bunch of cables, including ones that did support 1000Mbit.
>
>
>   
I think it is a hardware issue. Check both the switch and the cables. 
Could be with the switch. Most GB switches have colored lights to 
checkwhat speed each port is connected as. Is the uplink connection 
between the switch and the server running at 1000Mb. I assume your cable 
is ok because you do negotiate at 1000Mb  to the server. Nearly all my 
systems in the office here are Linux on 1 or 2 Netgear GB switches. My 
IA64 box at y desktop is showing 1000Mb with the e1000 driver. This is 
plugged into a wall outlet, and I believe all cables are either CAT 5E 
or CAT 6. I checked one of the servers, and it is ull 1000Mb using the 
tg3 driver.

A few years ago my desktop system at work (Digital Alpha) was connecting 
at 10Mb half duplex into a 100Mb switch. The problem was a bug in the 
switch firmware, but we were able to force 100Mb full duplex by setting 
the driver configuration in modules.conf. ethtool should be able to do 
this also.

The first thing I would do in your case is to check the cable. Most CAT 
5 cables can handle 1000Mb, but they are not guaranteed to and some 
cheap ones just don't have the extra wires. Try using a known good cable 
to the switch. Also test the switch with another system to make sure the 
port you are using on the switch negotiates at 100Mb with another computer.

Lastly, i you have a manage switch and have plugged in a recent version 
of XP or Vista, they have code that can detect the switch and upload 
Linux detection firmware onto the switch. That is why most of the 
laptops in my office are connected through another switch to prevent MS 
from hurting our Netgear switches :-)

-- 
Jerry Feldman <gaf at blu.org>
Boston Linux and Unix
PGP key id: 537C5846
PGP Key fingerprint: 3D1B 8377 A3C0 A5F2 ECBB  CA3B 4607 4319 537C 5846


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