Auto Negotiation Issue

[cbuster35]

Using a 3750V2 switch leaving the port set to the default ‘auto’ most (70%-80%) connected nodes negotiate at 100 / Half or 10 / Half. Only a few negotiate to Full duplex.

What would cause this type of behavior? The nodes range from Dell, HP, computers, along with Sharp and HP Printers.

Thanks

[glen.grant]

  That means most devices have their nics hardcoded to a speed/duplex and not set as auto/auto . 

[smehrnia]

hi,

are you sure your attached devices are set to auto negiotiate and they are not running at half duplex mode?

3750 ports configure themselves to operate at the speed of attached devices. if it is possible try changin the port of a device which successfully uses 100 full duplex with another half duplex port n see if things change or remain the same.

it is probabely something about the nodes.

plz Rate if it helped.

Soroush.

[Leo Laohoo]

I'll agree with Glen here.  There are only two events why the switch (like a recent generation 3750v2) will negotiate to half duplex.  And they are:

1.  When the remote end client(s) have configured the duplex settings manually; or

2.  When dealing with old clients or clients with old NIC firmwares.

[Richard Burts]

There is at least one more reason why the switch goes to half duplex when it is configured to negotiate duplex. If the switch is configured to negotiate speed and the negotiation of speed is not successful then the switch will go to half duplex.

HTH

Rick

[Leo Laohoo]

There is at least one more reason why the switch goes to half duplex when it is configured to negotiate duplex. If the switch is configured to negotiate speed and the negotiation of speed is not successful then the switch will go to half duplex. 

True.  Very true.

Curious though ... would this happen only to old NICs and/or firmwares or have you seen this event in newer clients? 

[Richard Burts]

This behavior is not limited to old clients. I have seen this behavior with recent clients. In fact I was looking at an incident where we saw this behavior on Friday.

HTH

Rick

[Leo Laohoo]

This behavior is not limited to old clients. I have seen this behavior with recent clients. In fact I was looking at an incident where we saw this behavior on Friday.

Hmmmm ... I'll keep a lookout.

I do remember a number of new HP desktops, when users log out, the interface negotiate to 10/half.

[cbuster35]

I found this to be true. The last network person was setting the client devices to 100MB full duplex. Was a nortel environment. Even hard coding to 100 full would let it go to half duplex?

I will change some back to auto/auto on Monday when I get back to work.

Thanks

[Leo Laohoo]

Even hard coding to 100 full would let it go to half duplex?

In some cases if you hardcode the speed and duplex setting at both sides, you will run the risk of CRC line errors.

[Joseph W. Doherty]

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Phil Robertson wrote:
I found this to be true. The last network person was setting the client devices to 100MB full duplex. Was a nortel environment. Even hard coding to 100 full would let it go to half duplex? 

If the other side is auto/auto, that interface should go to half duplex.

What would be abnormal, one side 100/full and and the other auto/auto, the auto side dropping to 10 Mbps too.