Date: Tue, 02 Feb 1999 22:57:02 -0800 From: Robert Clark <Clark@open.org> To: Greg Lehey <grog@lemis.com> Cc: peter kok <peter@sweda.com.hk>, Greg Black <gjb@comkey.com.au>, FreeBSD Questions <questions@FreeBSD.ORG> Subject: Re: Excessive collisions on Ethernet Message-ID: <3.0.6.32.19990202225702.0089e840@opengovt.open.org> In-Reply-To: <19990203144110.W1179@freebie.lemis.com> References: <36B7CC74.5C09913B@sweda.com.hk> <19990131110224.I8473@freebie.lemis.com> <19990131192548.24006.qmail@alpha.comkey.com.au> <36B7CC74.5C09913B@sweda.com.hk>
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Greg, I've seen weirdness like this before, but I can't bring the cause to the front of my brain at the moment. I seem to remember one case where a 10-base-T cable had the wrong polarity on the rx pair, and this was causing a station to miss its collision sense. Consequently it wasn't doing a good job of backing off early. Before anyone gets grumpy with me, I may have the details of the cable fault wrong. I also remeber a case where one wire of the rx pair was marginal, and the system functioned, albeit irrationally. At least once a year I run into someone using two 10-base-T nics on the same hub port. How? Some hubs have a port that is both a "regular" and "uplink" port. When two station are connected this way, the tx collisions slip in under the collison sense mechanism. It can be quite a good laugh when you try to explain why not to use both ports at once. ( I haven't seen a lan analyzer yet that will pinpoint this specific problem. ) zzzzzz... oops, I'm curious to see what it turns out to be. [RC] At 02:41 PM 2/3/99 +1030, Greg Lehey wrote: >On Wednesday, 3 February 1999 at 12:11:32 +0800, peter kok wrote: >> Greg Black wrote: >> >>>> In the last few days I've noticed a really high number of collisions >>>> on my Ethernet. There are only 5 machines on the network, 3 of which >>>> are barely active, yet I see: >>>> >>>> (allegro, running 2.2.6-STABLE) >>>> ed0 1500 <Link> 00.00.c0.44.a5.68 43729816 45 43861788 12 977828 >>>> ed0 1500 widecast allegro 43729816 45 43861788 12 977828 >>> >>> That's only 1.1%. >> >> i would like to know how do you measure this collision? > >This is output from netstat -bi: > >$ netstat -bi >Name Mtu Network Address Ipkts Ierrs Ibytes Opkts Oerrs Obytes Coll >ed2 1500 <Link> 00.80.48.e6.a0.61 358053 5 64720004 458435 0 320307968 8347 >ed2 1500 widecast freebie 358053 5 64720004 458435 0 320307968 8347 >lp0* 1500 <Link> 0 0 0 0 0 0 0 >tun0 1518 <Link> 479 0 38668 616 0 126099 0 >tun0 1518 widecast freebie 479 0 38668 616 0 126099 0 >tun1* 1500 <Link> 0 0 0 0 0 0 0 >tun2* 1500 <Link> 0 0 0 0 0 0 0 >tun3* 1500 <Link> 0 0 0 0 0 0 0 >sl0* 552 <Link> 0 0 0 0 0 0 0 >ppp0 1500 <Link> 56159 0 13257713 57910 0 32470985 0 > >BTW, I had to reboot freebie. Since then, the incidence of collisions >is *much* lower. There's something funny going on here. > >Greg >-- >When replying to this message, please copy the original recipients. >For more information, see http://www.lemis.com/questions.html >See complete headers for address, home page and phone numbers >finger grog@lemis.com for PGP public key > >To Unsubscribe: send mail to majordomo@FreeBSD.org >with "unsubscribe freebsd-questions" in the body of the message > > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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