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?
