em(4) on FreeBSD is sometimes annoying

Jack Vogel jfvogel at gmail.com
Sat Aug 2 23:01:38 UTC 2008

On Sat, Aug 2, 2008 at 1:40 PM, Martin <nakal at web.de> wrote:
> On Sat, 02 Aug 2008 12:55:53 +0200
> Torfinn Ingolfsen <torfinn.ingolfsen at broadpark.no> wrote:
>> Just to be sure: also if the first command you try on the interface is
>> 'ifconfig up'?
> Hello Torfinn,
> good point, no. The problem appears when the first thing called on this
> interface is dhclient (caused by ifconfig_em0="DHCP"). I could also
> provoke this behavior after the interface was once up had an IP and was
> working (ping). All I need to do is to disconnect the NIC from the
> switch when I type "/etc/rc.d/netif restart".
> I have noticed further strange effects here. The behavior seems to
> be even more complex.
> After I typed "/etc/rc.d/netif restart", I waited until I get "giving
> up" message. Then I plugged the cable in. After about 30 seconds the
> link LED was on. I noticed that at this point I couldn't get an address
> using DHCP.

Well DUH, the agent exited, thats why it said "giving up" :)
That ain't complex behavior, its behaving as designed.

> So I disconnected physically the NIC (no cable) and link LED was
> still on! ifconfig showed me "state: active" with no cable plugged in.
> After further 30 seconds the LED went off.
> I attached the NIC again to the switch again and after 30 seconds
> again I got some other effect. The link LED went on (status: active)
> and the data LED was permanently blinking (about 2,5 times a second). I
> pulled the cable again and now the link LED is still on and the data
> LED still blinking (since about 10 minutes already).

Ya, so the update is slow, the fact that the LED is blinking means you
have an autoneg failure, so again, its your switch not the NIC.

Let me guess, you have some 100Mb home router and you are trying
to plug a gig nic into it and forcing the speed maybe?

I asked for a hardware list, now that includes the switch.


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