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Bronze

how to disable auto- negotiation on port

Hi every body!

I just want to know how one can disable the auto-negotiation on switch's port? My book says configuring speed and duplex will disable the auto-negotiation.But i read somewhere auto-negotiation is disabled by configuring duplex mode.

thanks a lot!

2 ACCEPTED SOLUTIONS

Accepted Solutions
Hall of Fame Super Blue

Re: how to disable auto- negotiation on port

Sarah

Auto-negotiation is primarily concerned with duplex and not speed. If you disable auto-negotiation then the switch can still detect the speed based on the incoming electrical signal.

I have always worked on the assumption that if you want to disable auto-negotiation you should configure both speed and duplex explicitly.

Jon

Hall of Fame Super Blue

Re: how to disable auto- negotiation on port

Sarah

"I also belived that auto-negotiation only help decides the duplex mode."

Sorry if i gave you the wrong impression. Auto-negotiation uses Fast link Pulses (FLP) to determine both the duplex AND the speed.

However if auto-negotiation is disabled then duplex cannot be discovered ie. it must be hardcoded, but speed can be detected using other means eg. the incoming electrical signal.

So a better way to put it -

auto-negotiation on = duplex and speed both determined using FLP.

auto-negotiation off - duplex cannot be detected but speed can using different method.

Jon

4 REPLIES
Hall of Fame Super Blue

Re: how to disable auto- negotiation on port

Sarah

Auto-negotiation is primarily concerned with duplex and not speed. If you disable auto-negotiation then the switch can still detect the speed based on the incoming electrical signal.

I have always worked on the assumption that if you want to disable auto-negotiation you should configure both speed and duplex explicitly.

Jon

Bronze

Re: how to disable auto- negotiation on port

Thanks Jon!

I also belived that auto-negotiation only help decides the duplex mode. The speed can be determined either by ftp of auto-negotiation process or by simply electrial signals received from the port.

But then i found the following link which shows both speed and duplex mode are decided by auto-ngotiation process. please see the technology ability field in the link.

http://www.iol.unh.edu/services/testing/ge/training/1000BASE-T/ANEG_brief.php

===============================

Hall of Fame Super Blue

Re: how to disable auto- negotiation on port

Sarah

"I also belived that auto-negotiation only help decides the duplex mode."

Sorry if i gave you the wrong impression. Auto-negotiation uses Fast link Pulses (FLP) to determine both the duplex AND the speed.

However if auto-negotiation is disabled then duplex cannot be discovered ie. it must be hardcoded, but speed can be detected using other means eg. the incoming electrical signal.

So a better way to put it -

auto-negotiation on = duplex and speed both determined using FLP.

auto-negotiation off - duplex cannot be detected but speed can using different method.

Jon

Bronze

Re: how to disable auto- negotiation on port

Thanks Jon! you are very articulate as usual.

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