turning off auto-negotiation on gigabit interface
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Posted by noah davids on January 27, 2008, 11:36 am
Please log in for more thread options what does turning it off really do? -- Noah Davids Serendipity is a function of bandwidth E-mail: ndav1@cox.net Web: http://members.cox.net/~ndav1 | |||||||||||||
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Posted by Trendkill on January 27, 2008, 11:51 am
Please log in for more thread options Well, technically auto-negotiation is only for slower than gig settings, since a gigabit connection cannot be half-duplex. However, and per Cisco Best Practices, either auto/auto or gig/gig is fine, so long as you match on both sides. I have also noticed some NICs that do not have a gig/full setting, and therefore you must go gig/gig. I have also noticed other boxes that seem to have issues when configuring auto on both ends. The bottom line is, match on both sides, and look at vendor documentation to see what they recommend for their specific device. The above being said, I am not sure where you have seen that gig requires auto negotiation, as that is not correct. Perhaps it is for a specific server or hardware? Turning it off simply implies that the speed and duplex is hard set, and is not negotiated on that side of the configuration. Auto negotiation is required if the hardware/ server does not have gig/full as a set option, in which case both sides would be configured to negotiate to the optimal setting. | |||||||||||||
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Posted by stephen on January 27, 2008, 3:00 pm
Please log in for more thread options > > It is my understanding that the gigabit spec requires auto-negotiation,
so
> > what does turning it off really do?
> > > > -- > > Noah Davids > > Serendipity is a function of bandwidth > > E-mail: nd...@cox.net > > Web: http://members.cox.net/~ndav1 >
> Well, technically auto-negotiation is only for slower than gig > settings, since a gigabit connection cannot be half-duplex. negotiate is needed on 1000M to sort out the wiring, master / slave etc for 1000 Base-T. It doesnt set the speed (unless the other end is slower), but it does set up the interface. However, > and per Cisco Best Practices, either auto/auto or gig/gig is fine, so
> long as you match on both sides. I have also noticed some NICs that > do not have a gig/full setting, and therefore you must go gig/gig. I > have also noticed other boxes that seem to have issues when > configuring auto on both ends. The bottom line is, match on both > sides, and look at vendor documentation to see what they recommend for > their specific device. > > The above being said, I am not sure where you have seen that gig > requires auto negotiation, as that is not correct. the reference comes from the IEEE standard - auto negotiation is a required part of the standard for GigE 1000 Base-T, not just optional as it was with 100 Base-Tx. remember that as part of setup on 1000 Base-T, the 2 ends negotiate to sort out pairing etc, so this sort of makes sense. as a practical issue, some devices REQUIRE a linked device to be using auto at Gigabit, or they dont work, even with fibre ports. For example, a recent wierdness trying to bring up fibre GigE links to a Foundry MLX-4 turned out to be the SDH mux it was plugged into was set for no negotiate, and the Foundry insists that auto is enabled. the really annoying bit was that the MLX port had a "negotiate" option, but the only allowed setting was "yes". When we had a mismatch, the Foundry lit the green light against the interface on the card, but no L3 traffic..... Serious head scratching until we ignored the lights and went thru the logs. i have other similar issues on GigE - so i suggest that if you have a GigE or a 10/100/1000 device, you might need "auto". Perhaps it is for > a specific server or hardware? Turning it off simply implies that the
--
> speed and duplex is hard set, and is not negotiated on that side of > the configuration. Auto negotiation is required if the hardware/ > server does not have gig/full as a set option, in which case both > sides would be configured to negotiate to the optimal setting. Regards stephen_hope@xyzworld.com - replace xyz with ntl | |||||||||||||
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Posted by Thrill5 on January 28, 2008, 12:27 am
Please log in for more thread options
>> It is my understanding that the gigabit spec requires auto-negotiation,
>> so >> what does turning it off really do? >> >> -- >> Noah Davids >> Serendipity is a function of bandwidth >> E-mail: nd...@cox.net >> Web: http://members.cox.net/~ndav1 >
> Well, technically auto-negotiation is only for slower than gig > settings, since a gigabit connection cannot be half-duplex. However, > and per Cisco Best Practices, either auto/auto or gig/gig is fine, so > long as you match on both sides. I have also noticed some NICs that > do not have a gig/full setting, and therefore you must go gig/gig. I > have also noticed other boxes that seem to have issues when > configuring auto on both ends. The bottom line is, match on both > sides, and look at vendor documentation to see what they recommend for > their specific device. > > The above being said, I am not sure where you have seen that gig > requires auto negotiation, as that is not correct. Perhaps it is for > a specific server or hardware? Turning it off simply implies that the > speed and duplex is hard set, and is not negotiated on that side of > the configuration. Auto negotiation is required if the hardware/ > server does not have gig/full as a set option, in which case both > sides would be configured to negotiate to the optimal setting. Actually the specification for 1000BaseT REQUIRES autonegotiation. But I have seen issues where auto/auto did not work but this was always due to driver issues on the device. Updating the driver on the PC/Server always fixed the problem. | |||||||||||||
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Posted by Trendkill on January 28, 2008, 5:58 am
Please log in for more thread options >
> > > > >> It is my understanding that the gigabit spec requires auto-negotiation,
> >> so > >> what does turning it off really do? >
> >> --
> >> Noah Davids > >> Serendipity is a function of bandwidth > >> E-mail: nd...@cox.net > >> Web: http://members.cox.net/~ndav1 >
> > Well, technically auto-negotiation is only for slower than gig
> > settings, since a gigabit connection cannot be half-duplex. However, > > and per Cisco Best Practices, either auto/auto or gig/gig is fine, so > > long as you match on both sides. I have also noticed some NICs that > > do not have a gig/full setting, and therefore you must go gig/gig. I > > have also noticed other boxes that seem to have issues when > > configuring auto on both ends. The bottom line is, match on both > > sides, and look at vendor documentation to see what they recommend for > > their specific device. >
> > The above being said, I am not sure where you have seen that gig
> > requires auto negotiation, as that is not correct. Perhaps it is for > > a specific server or hardware? Turning it off simply implies that the > > speed and duplex is hard set, and is not negotiated on that side of > > the configuration. Auto negotiation is required if the hardware/ > > server does not have gig/full as a set option, in which case both > > sides would be configured to negotiate to the optimal setting. >
> Actually the specification for 1000BaseT REQUIRES autonegotiation. But I > have seen issues where auto/auto did not work but this was always due to > driver issues on the device. Updating the driver on the PC/Server always > fixed the problem. After looking more in depth at the Best Practices, you are indeed correct, although I was talking about specific speed/duplex settings and did not realize there was a higher level term of 'autonegotiation' for flow control and other interface settings (does not include speed). Apparently auto-negotiation is what I was referring to, and autonegotiation (without the hyphen) is the broader topic. Here is the link, and here are some excerpts: "Unlike autonegotiation with 10/100-Mbps FE, GE autonegotiation does not involve the negotiation of port speed. Also, you cannot issue the set port speed command in order to disable autonegotiation. GE port negotiation is enabled by default, and the ports on both ends of a GE link must have the same setting. The link does not come up if the ports at each end of the link are set inconsistently, which means that the exchanged parameters are different." "The configuration of autonegotiation is much more critical in a GE environment than in a 10/100 Mbps environment. Only disable autonegotiation in these situations: * On switch ports that attach to devices that are not able to support negotiation * Where connectivity issues arise from interoperability issues http://www.cisco.com/en/US/products/hw/switches/ps700/products_white_paper09186a00801b49a4.shtml http://www.cisco.com/en/US/tech/tk389/tk214/technologies_tech_note09186a0080094781.shtml http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a00800a7af0.shtml | |||||||||||||
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> what does turning it off really do?
>
> --
> Noah Davids
> Serendipity is a function of bandwidth
> E-mail: nd...@cox.net
> Web: http://members.cox.net/~ndav1