Network manager does not allow the speed of a wired ethernet connect to be set

[Adam J. Lincoln]

As far as I can tell, ethernet cards usually behave just fine if allowed to autonegotiate speed and duplex. Sometimes, though, this doesn't work. A user should be able to force, for example, 10BaseT/half duplex for their ethernet connection(s) by right clicking on the network-manager applet, going to Edit Connections..., the Wired tab, editing the interface in question, and finding the option in, say, the "Wired" tab on the "Editing Auto eth0" window that pops up.

I ran into this when dealing with an old wired network at work (a university). Autonegotiation fails under all operating systems and all ethernet cards (that I tried), and the well known solution in other OSes is to manually set the speed/duplex to 10BaseT/half. In OS X, e.g., this is right where you'd expect it, near the options to setup your wired connection manually instead of using DHCP. On my ubuntu jaunty system, though, I had to do

sudo ethtool -s eth0 autoneg off speed 10 duplex half

then put it in my /etc/rc.local to make it persist. Wouldn't this fit in just fine in nm-applet?

So for completeness:
$ lsb_release -rd
Description: Ubuntu 9.04
Release: 9.04

$ apt-cache policy network-manager-gnome
network-manager-gnome:
  Installed: 0.7.1~rc4.1-0ubuntu2

Expected to find options to set ethernet speed/duplex via network manager, didn't find it.

Had to do it via command line.

[Glen Turner (gdt-gdt)]

As operator of a university network let me say that most people misunderstand ethernet autonegotiation. When they set speed and duplex they don't realise that setting implicitly disables the NWay autonegotiation protocol at speeds under 1Gbps. Thus they do not think to set exactly the same parameters on the partner interface. This misunderstanding is a major cause of "late collision" errors. Those errors radically reduce TCP goodput.

It would be nice for nm-connection-editor to offer speed=10Mbps, duplex=half as a single option for when autonegotiation fails so that people can get basic connectivity. This is the speed and duplex assumed when the NWay autonegotiation protocol is not seen, and thus is always safe to use when the partner interface remains running autonegotiation. Other options could he hidden in another panel, which reminds people to also manually alter the configuration of the partner interface.

In this way Ubuntu and GNOME could offer a workable solution for a repeatedly-failing autonegotiation whilst not increasing the amount of network host misconfiguration.

[Marius B. Kotsbak (mariusko)]

Could you please open an upstream bug report about this:

https://bugzilla.gnome.org/enter_bug.cgi?product=NetworkManager