em(4) on FreeBSD is sometimes annoying

Martin nakal at web.de
Sat Aug 2 05:00:20 UTC 2008

On Fri, 1 Aug 2008 05:42:24 -0700
Jeremy Chadwick <koitsu at FreeBSD.org> wrote:

Hi Jeremy,

> Most commonly what you're reporting is the result of a switch upstream
> which isn't fully compatible or properly doing 802.3u auto-neg.

It is attached to a cheap switch here. Also at my office it is not
coming up. And I have NEVER this problem when the laptop is already
plugged in.

> Rebooting the machine (thus tearing down link hard, and resetting the
> entire chip) often works in this situation.  You can also try setting
> the speed and duplex (media and mediaopt) in your ifconfig_emX line in
> rc.conf to see if that helps (on some switches it does).

This is what I get, when I plug it in and try to configure something:

# ifconfig em0 mediaopt full-duplex
ifconfig: SIOCSIFMEDIA (media): Device not configured

But it accepts up, down and even inet <address>. LEDs are off and still
"no carrier".
> The behaviour you're reporting I've seen on old 3Com XL 509x cards with
> Cisco switches, for example.

I've heard of the autonegotiation problem, but it rather looks to my as
if something is getting initialized during BIOS boot and FreeBSD is not
doing it correctly.

> I have a Thinkpad T60p.  I'll try booting FreeBSD on it next week and
> see if I can reproduce the behaviour.  I'll also include what switch
> brands/models are being plugged into.

Once again. I made a mistake describing the problem. I'm really sorry
for this. The interface actually appears in the ifconfig list, but I
cannot get it up. It always shows "no carrier". No matter what I try.


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