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Community Member

Lan speed and duplex negotiation


when you have speed and duplex set manualy would this stop the negotiation with the other site ?


Re: Lan speed and duplex negotiation

It should, but it's not always the case.

Depending on the model of the switch, what it's connecting to (vendor, model, and firmware) sometimes they work better with both sides set to auto, sometimes it requires that both sides be set manually to the desired speed & duplex.

Most of the time, setting one side will cause the other side to properly match up.

What do you have, and what are you connecting to?

Good Luck


Community Member

Re: Lan speed and duplex negotiation

thank you for the reply

i had the folowing problem which is solved

router with manual setting speed 100, duplex full

conected to an uknown switch witth increasing input errors.

By changing all setting to auto,

speed and auto duplex got the same settings 100 full duplex but errors disapeared

My explanation to this (I have no visbility to the switch )by schanging settings to auto, negotiation started and switch changed the setting to 100 full from probably default 100 half.

and from here comes my question would be by setting the ethernet to manual will disable nogatiations ?


Re: Lan speed and duplex negotiation

simple rule of thumb , if one end is auto the other end must also be auto . If one end is hardcoded the other end must be hardcoded. If one end was hardcoded to say 100/half and the other end is auto it would "probably negotiate" correctly as the auto end will always sense the speed correctly but cannot negotiate the duplex without the far end being auto thus it defaults to half duplex. If one is hardcode to 100/full and the other end is auto this is a mismatch and will cause errors.

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