"Forcing" gigabit link operation

googlegroups · 2006-03-20T21:02:20+00:00

I know Rick's words to be the truth, and yet I regularly see NIC setupinterfaces that purport thier ability to "force" gigabit operation.Like this one: 's the deal with these control panels?My guess is that the NICs are still autonegotiating, but restrict thebits advertised in the TAF to just the gigabit modes.Is that correct?Secondarily, can anyone offer perspective on why-oh-why systems/networkpeople everywhere seem to think autonegotiation is totally unreliable?I can count the number of times I've seen a genuine negotation failurewith my fingers, and those invariably involved pre-802.3u transceivers.OTOH, the number of links I've seen screwed up due to force-happyadministrative error are myriad./chris

Mar 20, 2006 25 Replies

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Rick Jones 20 years ago

Nah, then people would have been asking how to get their networks out of binding arbitration :)

rick jones

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Rich Seifert 20 years ago

I doubt that. The only Ethernet system that ever used a special "jam" signal was on early Xerox experimental equipment (i.e., Alto workstations). I doubt you used those (although it is entirely possible; I had an Alto on my desk in 1979).

By the time DIX Ethernet was released (essentially identical to

10BASE5), the special jam was gone.

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Manfred Kwiatkowski 20 years ago

A Longshine dual-speed hub negotiating 100-full to a Procurve 4000M.

As to the 10mbit issues:

3Com SuperStack II 1100 will negotiate 10-full but connected to some 3C905s will experience a duplex mismatch.

VIA-Rhine vs. ATI Centrecom 3600 hubs

Just from the top of my memory.

-- Manfred Kwiatkowski snipped-for-privacy@zrz.tu-berlin.de

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glen herrmannsfeldt 20 years ago

As I understand it, the 3C905, 3C905B and 3C905C are completely unrelated, other than the similarity in model number.

I once tried to get Solarix-x86 to work on a machine with a

3C905C, but it didn't notice at all. (In addition, I had a bad cable.)

I also used to have a 3C250, I believe on of the earlier models of fast ethernet (100 only) repeaters. I never had any problems with that one.

-- glen

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Stephen Sprunk 20 years ago

I don't know which model number(s) the problem was with, but I remember running a datacenter when they were popular, and I had this conversation several times per day, every day:

server admin: Your switch is broken! My server is coming up as [10/full |

100/half] instead of 100/full! me: Is it a 3com NIC? server admin: Yes me: Go get the latest Windows drivers. [ time passes ] server admin: It still doesn't work! You didn't fix anything! me: Did you reboot after you installed the drivers? server admin: Um, no. [ time passes ] server admin: It works now, nevermind.

If they were only repeaters, auto-duplex shouldn't have been an issue. I did see a few NICs that insisted on coming up at 10Mb/s when the switch supported 100Mb/s, though.

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