Date: Sat, 22 Oct 2011 14:48:21 -0700 From: Kevin Oberman <kob6558@gmail.com> To: perryh@pluto.rain.com Cc: freebsd-stable@freebsd.org, freebsd@jdc.parodius.com Subject: Re: 8.1 xl + dual-speed Netgear hub = yoyo Message-ID: <CAN6yY1vjHHT%2BYoqO6DQPytO-SectkM9V3pJN=uKYHgv26h5LDQ@mail.gmail.com> In-Reply-To: <4ea2e874.XnQpdCknhYCB39Py%perryh@pluto.rain.com> References: <4ea18916.IBAr0lF5RCzEYn6G%perryh@pluto.rain.com> <4EA12D26.4020104@my.gd> <4ea2b29c.QmX94UmzdHW1HSBe%perryh@pluto.rain.com> <20111022052952.GA2371@icarus.home.lan> <4ea2e874.XnQpdCknhYCB39Py%perryh@pluto.rain.com>
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On Oct 22, 2011 2:21 AM, <perryh@pluto.rain.com> wrote: > > Jeremy Chadwick <freebsd@jdc.parodius.com> wrote: > > > 1) I think you misunderstand what product it is you own. You have > > a hub, not a switch. This is confirmed by the fact that auto-neg > > chooses to negotiate half-duplex. Instead, you went later and > > messed about trying to force full-duplex, which isn't going to > > work on a hub. The fact you even tried it has many implications. > > Just one implication, really: I tried "everything". I know > that some gear from this era did not autonegotiate speed/duplex > correctly, so when the autonegotiated configuration didn't work > I tried both explicit duplex settings at 100Mb. (I don't _need_ > full-duplex, but tried it for completeness.) > > > If you want full-duplex, you need an actual switch. Netgear > > refers to "hubs" as actual hubs, and "switches" as actual > > switches. Do you know the difference? > > Yep, including the fact that a true hub can't do speed translation > because it doesn't buffer the entire packet -- it retransmits each > bit as received. This device -- despite being called a hub -- has > to contain at least one packet worth of buffering so that it can > retransmit a packet received at one speed to the ports that are > operating at the other speed. > > I also know, from direct experience with attempting to sniff traffic > (via tcpdump, wireshark, etc.), that this model of so-called hub > does _not_ unconditionally retransmit everything received from one > port to all of the other ports, even if all are operating at the > same speed. It seems to be some kind of hub-switch hybrid. > > > This is the first time I have ever seen a hub in use in almost > > 10 years. > > Most of the gear here is in the museum category. The mail server > is a Sun-3/60 that is over 20 years old. It ain't broke. (That's > why there's a 10Mb hub, whose AUI uplink is connected to a 10Base-2 > transceiver.) One of FreeBSD's advantages is that it tends to run > well on old hardware. > > > 2) There is no guarantee your NIC is fully compatible > > (negotiation-wise) with the hub. Vendor interoperability problems > > were extremely common "back in the day" (you're using a 3Com NIC > > from the mid-to-late 90s ... > > Yep, see comment re #1. However, if it were a negotiation problem, > I would have expected hard-setting the NIC to 100 to have fixed it; > the hub was showing that port as operating at 100. (BTW this model > of hub is about as old as the NIC.) > > > You can either replace the NIC with something else, or replace the > > hub. IMHO, I would replace both. > > I can replace the hub easily enough -- I have a 100-only Netgear > that _is_ a true hub (has been used successfully for sniffing) -- > although I suppose being the same brand and about the same age it > may have a similar compatibility problem :( > > Replacing the NIC is a bit more of a problem, because it's built > onto the mainboard. I do have some Intel NICs, and I _think_ the > box has an unused slot. > > > 5) The xl(4) driver is extremely old and basically is not maintained > > any longer. I would not be surprised if this was a driver bug. > > It had occurred to me that there might be a driver problem -- that > was one reason for posting -- although all I found with Google was a > watchdog reset problem that was fixed long enough ago that the fix > surely would have been in 8.1. However if the driver is no longer > maintained, and swapping out the hub doesn't fix it, it seems I may > be reduced to playing musical NICs. Wow. it's 1985 again. O remember those 10/100 hubs. They were a royal pain! If I remember right, they kept costs down by building in half of a switch. Traffic from a 10 port to a 100 port was buffered, but there was no forwarding table and all packets were forwarded to all ports. Total crap! I also remember that SOME hubs of that era had series problems if the cable was too short. You mentioned using a short cable. Have you tried a longer one? I seem to recall that 3 meters was the minimum, but it was so long ago that my memory is a bit fuzzy. R. Kevin Oberman, Network Engineer Retired kob6558@gmail.com
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