The biggest problem with duplex had to do with 100mb. Cisco (and a lot of other companies) decided in their infinite wisdom that at 100mb if auto-negotiation fails, to use half duplex as the default. So if you have both sides at auto, or both sides hard-set it's all good. But if one side is hard-set and the other is auto, a lot of times the auto device will come up 100/Half. These days at 1Gb+ Full-Duplex seems to be the 'default' for auto-negotiation failures. Ken Matlock Network Analyst Exempla Healthcare (303) 467-4671 matlockk@exempla.org -----Original Message----- From: Joe Abley [mailto:jabley@hopcount.ca] Sent: Tuesday, December 08, 2009 8:14 AM To: sthaug@nethelp.no Cc: nanog@nanog.org Subject: Re: Linux shaping packet loss On 2009-12-08, at 15:01, sthaug@nethelp.no wrote:
Won't say I'm an expert with TC, but anytime I see packet loss on an interface I always check the interface itself...10% packet loss is pretty much what you would get if there was a duplex problem. I always try to hard set my interfaces on both the Linux machines and Switches.
Used to set everything hard five years ago. Nowadays auto works just fine most of the time.
I find there is a lot of hard-coded wisdom that hard-coded speed duplex are the way to avoid pain. The last time I saw anybody do a modern survey of switches, routers and hosts, however, it seemed like the early interop problems with autoneg on FE really don't exist today, and on balance there are probably more duplex problems caused by hard-configured ports that are poorly maintained in the heat of battle than there are because autoneg is flaky. I've also heard people say that whatever you think about autoneg in Fast Ethernet, on Gigabit and 10GE interfaces it's pretty much never the right idea to turn autoneg off. I am profoundly ignorant of the details of layer-2. It'd be nice to have more than vague rhetoric to guide me when configuring interfaces. What reliable guidance exists for this stuff? Joe