A great little tool for Windows systems is the command “netstat -e“. I shall explain.
A bane of of the network is the insidious duplex mismatch issue. This is when, through either autonegotion or auto-detection, one end of two cabled devices think the link is full duplex, and the other end thinks it is half duplex. During this condition, the link will work, but will be much slower (limited to around 5-15 Mbps on a Fast Ethernet 100 Mbps link).
The usual method for detecting mismatches is to check the error counters. Depending on which side you’re looking at, you’ll see runts, late collisions, or other Ethernet errors. This is especially true if you try to push any significant amount of traffic through a duplex mismatched link, so a high error count makes it easy to spot when you know what to look for.
However, the errors may not be as frequent on one end of the Fast Ethernet link versus the other, depending on which direction the traffic is flowing and which end is set for half and which end is set for full. So if a mismatch is suspected, it maybe a good idea to check both the switch port and the servers as well for Ethernet errors.
For Linux/Solaris/BSD/etc., the “ifconfig -a” will typically display any Layer 2 errors on the system’s interfaces. However, for Windows, the comparable command in Windows (ipconfig) does not show error information. Fortunately there is another way .
In Windows (XP/2000/Server 2003/Vista/etc), “netstat -e” will show you the Ethernet stats on an all Interfaces for the Windows system. If you see any errors, the culprit may very well be a duplex mismatch.
Also, make sure to check the switch port for errors.
I have seen times where a system does not show errors, but you will see errors on the switch.
If you have Gig-E RJ45 ports, setting all interfaces to AUTO has worked pretty well for us.
-Ron
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