Many Network Admins ask for help with server communication problems and more often than not they are due to speed and/or duplex setting differences between the computer and the switch port it is plugged into.  By default, a 10/100Mb switch will be configured to Auto-Sense the speed and duplex settings it should use on each port based on the capabilities that the computer plugged into it can handle.  Each port has the following  configuration options for speed:  100/10/Auto, and the following configuration options for duplex: Full/Half/Auto.  Likewise, each 10/100Mb network interface card (NIC) has the same configuration options.  The default for both the switch ports and the NICs is Auto/Auto.

This leaves quite a bit of important configuration up to the hardware to decide on.  In our experience in the ITCS LANNOS group, this auto-configuration has been the source of more problems than it's worth.  In order for things to work correctly and efficiently, the switch port and the NIC have to agree on what speed and duplex configuration they should use.  Usually they can happily agree on the speed, but the duplex seems to be a major point of contention.

To eliminate this auto-configuration from the equation, we are in the practice of forcing the speed and duplex on every switch port we have a server connected to, and matching those setting on the NIC.  We never use Auto/Auto on any server.  Some things that we have seen when using Auto/Auto and it fails to negotiate properly include: client disconnects from the server, poor performance either uploading to the server or downloading from the server, slow logins, intermittent server to server communication problems.  These conditions will increase in severity as the load on the server increases.

In ITCS LANNOS all of our servers are Dell servers with Intel 10/100 NICs installed.  All of our NICs are configured for 100/Full and all of our switch ports are also configured for 100/Full.  We have heard reports that Compaq NetFlex 10/100Mb cards have problems at Full duplex when connected to Cisco Switches, so if you experience this problem, try Half duplex.  To have the switch ports configured, we send a configuration request to ITCOM that includes the IP address of the switch in question, the port number, and the desired port speed and duplex configuration we would like.  To configure the NICs, we use the Boards menu item in  INETCFG to access the properties of our NIC.  If you do not see the speed and duplex options in the properties of your NIC, you may need a newer NIC driver.  Contact your NIC provider for more information.

Have you ever tried to build a new server, or upgrade an existing server, by booting it to DOS and using VLMs to connect to the source files on ITD-NW1?  Ever lost your connection to ITD-NW1 part way through the install?  This is usually due to a duplex mismatch.  Most DOS NIC drivers are capable of correctly auto-negotiating the speed of a switch port connection, but few (in my experience) can do so with the duplex setting.  It appears to me that they default to half duplex without even trying to determine if that agrees with the switch port it is plugged into.  So when I need to down a server to DOS, that is plugged into a 100/Full switch port, and connect to ITD-NW1 with VLMs, like when upgrading to NetWare 5.1, I need to be able to tell the DOS driver to use Full duplex.

Since all of or servers are Dell, with Intel NICs, we use the same DOS driver for all of them, E100BODI.LAN.  In the case of that driver, in order to get it to use Full duplex, we needed to add the lines "SPEED = 100" and "FORCEDUPLEX = 2" to the Link Driver section of the NET.CFG file in the NWCLIENT directory.  Other drivers may work the same, or may require that you use other methods to force the duplex to 100.  One possible source of finding out how to force your duplex setting is to look in the .INS file with the same name as the driver file (i.e. E100BODI.INS).  The .INS file is a text file that should contain information about all of the possible configuration options for that driver.

We used to have lots of problems installing and upgrading servers from ITD-NW1, but since we resolved the duplex issue using the DOS drivers, now we do all of our installs and upgrades this way.

We hope this document will help some of you correct some problems and make your work a little easier.  If you have questions or comments, please email netware.support@umich.edu.

Thank you.