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New Member

Duplex settings

On every Cisco course they told me to configure the duplex-settings on a switchport from the standard auto to a fixed half or full setting.

I experienced this always as good practice, because i had several cases where this "fixing" solved big throughput problems. Until today.

Today I had complaints of two users. The NIC's (Intel Pro100 S) in their WinNT-stations are configured to fixed 100Mbit and fixed full duplex. The switch(C3548-XL) has its ports configured fixed in 100/full. When I checked the switch, I saw the input/output error-counters go up on these two ports.

When I altered the duplex-setting from fixed to auto, the problem stopped. However, when I did a show interface, I saw that the negotiatian resulted in a full duplex setting! So, I changed it back to fixed full duplex and the problem was there again. Back to auto it was solved again.

Does anyone have a good explanation of this duplex-setting behavior? I noticed that problems with auto-duplex do more often happen with some branches of NIC's then with others. Is there a "preferrable" branch of NIC's when you use Cisco-switches?

New Member

Re: Duplex settings

This seems to be a bug in Intel NIC. There is a similar kind of bug in Intel NIC for Laptop PCMCIA. You can also check in Intel website or via e-mail.


Re: Duplex settings

You would think after all these years these manufacurers could make something that could consistently use the auto setting without a problem .