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Auto-Negotiate verses hard set

I have many users connected to my Cisco switches, that refuse to hard set their workstation to the proper settings. If I set the switch port to 10/half, they will leave their workstation to auto and wil not allow anyone to change these setting. I am forced to leave the switch port to auto as well, as leaving one end on auto just causes too many issues.

Is there a way to display the errors caused by this mismatch? (without adding a sniffer to the mix)

Is there a way to determine how many times the Cisco switch had to re-negotiate the settings when left to auto?

Exactly what events require the auto-negotiation feature to re-negotiate?

How many times a day could this auto-negoitation feature have to re-negoitiate?

Thanks to ANYONE who can provide assistance.

Cisco Employee

Couple of comments first.

- If you hard set your switch port to 10/half, the other end will always (well, should) 'default' to 10 half.

- Once you hard set a port or NIC, that port or NIC will NO longer sending Auto-negotiation parameters in an embedded code word to the connected device (Per IEEE spec)

- Auto to 10/half should not cause any issues. The AUTO configured side will see no auto-negotiate parameters, only NLP and not FLP and set the speed 10 meg

- You will *always* get errors when using half-duplex. Half-duplex will result in errors due to the collisions.

Now, I do not see how setting one side to Auto and the other to 10/half causes, what problems does it cause?

Depending on the duplex setting. Full-duplex should see very few errors (in the order of 10s a day at most).

See for more details

The switch will not re-negotiate unless there is link down situation or a change in the configuration on the switch for speed/duplex.

I believe the only events that require a port to re-negotiate or link down or change in FLP, NLP or new code word? Double-check the spec.

You are going to hear a lot of replies about always hard setting both the switch and the NIC. In my opinion, I see no problem using auto-negotiation. In the past years or so, with the latest NIC drivers and Switch software, I have not run into many NEW issues (see for an issues list)

I generally see customers have more problems trying to hard set the NIC rather than just using Auto-negotiation these days.


You can look at errors by using the command "show port counters" and or show counters slot/port . It will tell how many errors you seeing it won't tell you anything about how the negotiation went . You are better off leaving the switch at auto if that is what the users are using . Generally the auto feature works better than it used to but there are still many bugs with certain nic cards , if you have access to CCO look up troubleshooting nic problems , they give you a whole list of certain nic cards and the known problems with these cards . If you are having problems make sure the nic card drivers are at the latest version .


Thanks for the responces. And I do agree with the information provided.

Little update - I support Win 95, 98, NT, 2000, Sun Solaris Unix, Red Hat versions (changing all the time), Apple Mac's running TCP/IP and various other OSes. MOST users will not allow the Network Engineers to change the settings on their systems (MANY reasons why). Anyway, I have hard coded the switch ports to 10Mbps / Half duplex. The link back to the back bone is only 100 Full. I have 125 users on these switches so leaving it to auto will only clog the line back to the backbone. (Changes are on the way!!!)

It turns out Apple WILL NOT auto itself to 10/half - It MUST be 10 Full or nothing.

Thanks again.


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