kern/140326: em0: watchdog timeout when communicating to windows using 9K MTU

[Maxim Sobolev]

The following reply was made to PR kern/140326; it has been noted by GNATS.

From: Maxim Sobolev <sobomax at FreeBSD.org>
To: Jack Vogel <jfvogel at gmail.com>
Cc: freebsd-gnats-submit at FreeBSD.org
Subject: Re: kern/140326: em0: watchdog timeout when communicating to windows
 	using 9K MTU
Date: Fri, 06 Nov 2009 00:30:33 -0800

 Jack Vogel wrote:
 > Good, that's a start. Now, is there a switch of some sort involved or 
 > are you going
 > back to back? Some switches have problems with jumbo frames, there are also
 > some vendors (including our's) interfaces that do not support jumbo 
 > frames, so
 > you need to check on that also (I mean the RT).
 > 
 > I will check on the Intel adapter tomorrow.
 
 Yes, there is switch involved (Cisco/Linksys EG008W ver.3), but I don't 
 think it's related. The problem has really escalated when I installed 
 Windows 7 on this machine yesterday. Before that the same machine with 
 Realtek was running Vista and this problem had happened to me only once 
 or twice in two weeks with the same MTU on both ends. And from the 
 capture it seems like the very specific condition causes this. 
 Unfortunately this box is a gateway for a network, so that I cannot 
 replace hub and try to reproduce the issue.
 
 -Maxim