kern/110561 "em" driver shuts down interface when "ifconfig media 100baseTX" is invoked

[Infraservice hostmaster]

| On 3/20/07, Infraservice hostmaster <hostmaster at infra-service.ca> wrote:
| > | On Tue, Mar 20, 2007 at 07:40:10AM +0000, Infraservice hostmaster wrote:
| > | > The following reply was made to PR kern/110561; it has been noted by GNATS.
| > | >
| > | > From: Infraservice hostmaster <hostmaster at Infra-Service.ca>
| > | > To: bug-followup at freebsd.org
| > | > Cc:
| > | > Subject: Re: kern/110561 "em" driver shuts down interface when "ifconfig media 100baseTX" is invoked
| > | > Date: Tue, 20 Mar 2007 03:31:54 -0400 (EDT)
| > | >
| > | >  |
| > | >  | Synopsis: :"em" driver shuts down interface when "ifconfig  media 100baseTX"  is invoked
| > | >  |
| > | >  | State-Changed-From-To: open->closed
| > | >  | State-Changed-By: remko
| > | >  | State-Changed-When: Tue Mar 20 06:42:06 UTC 2007
| > | >  | State-Changed-Why:
| > | >  | This is not a bug, this is a problem in the negotiation on the other
| > | >  | side. If the switch you are attaching to is not supporting the fixed
| > | >  | setting of the speed and duplex settings or incorrectly negotiates then
| > | >  | this is not a problem of the driver nor the card but a switching
| > | >  | problem. Please try to findout FIRST what the real problem is and THEN
| > | >  | get back to me if this really is a FreeBSD problem (Discuss this on the
| > | >  | networking mailinglist please >
| > | >  | http://lists.freebsd.org/mailman/listinfo/freebsd-net/).
| > | >
| > | >     This happens to every interface we tried it on!
| > |
| > | Right, which is consistent with the switch failing to negotiate.
| >
| >         wrong, each interface connects to distinctly different devices
| >
| >         one is a cisco adsl router, another is a FBSD 6.2 box with an
| >         Intel fxp card - it ifconfigs media/mediaopt just fine BTW
| 
| So, if each 'distinctly different device' can't handle forcing the speed
| then Kris's assertion still holds.
| 
| Our test group at Intel has a wide range of hardware, and they do
| extensive tests on forcing speed/duplex, I am unaware of any
| outstanding bugs on this issue.


	I think i am cunfused by this difference between what i see
	with a fxp interface:

	media: Ethernet 100baseTX <full-duplex>
	status: active


	... and an em interface:

	media: Ethernet 100baseTX <full-duplex> (autoselect)
	status: no carrier


	I've not previously seen "(autoselect)" appended after doing
	"ifconfig <interface> media 100baseTX mediaopt full-duplex"
	to my recollection.


	Is a defective ethernet cable a possible cause even though
	it seems to pass packets just fine?