I have a point to point connection by fiber with 1000BASE-X Ethernet. The rate is always at 1 Gbps, and I believe full-duplex would not be a problem.

Since the link is point to point, it seems that there is no reason to "negotiate" speed or duplex.

Therefore, can I just disable the Auto-Negotiation function?

  • There is no negotiation on fiber ethernet connections; it connects at 1 Gbps, or it doesn't. Negotiation really isn't any issue since, even on copper interfaces, it only happens right when the interface comes up.
    – Ron Maupin
    Mar 30, 2017 at 22:21
  • Great! That means I can disable Auto-Negotiation and not worry about it.
    – Abe
    Mar 31, 2017 at 0:15
  • Why bother? You will never notice it, it does nothing bad, and there are things that may expect it. In networking, as in many things, "If it ain't broke, don't fix it!" is excellent advice.
    – Ron Maupin
    Mar 31, 2017 at 0:52
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin
    Feb 19, 2018 at 3:51
  • Chiming in. Today we had a 1000base-sx sfp in an sfp+ port on an extreme/avaya switch which didn't want to talk to its neighbor (some hpe gear) unless we enabled autoneg. Not sure what the settings on hpe were. 😩
    – Marki
    Mar 2 at 20:25

3 Answers 3


The link probably doesn't need auto-negotiation, but you probably should not change the default without a good reason. There is nothing about having it configured that will cause you any problem, and it only happens when the link comes up. It takes virtually no time to happen. You really don't want to make network changes, just because. "If it ain't broke, don't fix it!"


If you disable negotiation then you must do it at both ends as it is not Auto-Detect. Negotiation means the two ends negotiate the connection that is they talk, so If you change only one end the other end will attempt to negotiate get no answer and decide what to use on its own. With 100Meg ports this is always 10Meg, Half duplex as (IMHO) that is the most likely if the device does not negotiate. The bad thing is that with 100M Full/10M Half with a lightly loaded link it still works so you move on and when lots of traffic hits the link it goes down.

I've not tried this on 1000 Meg or 10000 Meg links so I don't know if this still happens. I'm not really sure how full/half duplex applies to a 1000Meg link - as on copper I thought it used all four pairs to transmit - so it seemed to me to be inherently half-duplex but I'd think it is point to point and negotiates who will talk next that is not collision sensing. If so then the Half duplex setting would have a different meaning and you might find it cannot be applied in the config.


If your network now are working well, you don't have to change it.

  • Can you expand this answer a bit more, it's rather vague.
    – Baldrick
    May 5, 2017 at 14:39

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