Should I use Half Duplex or Full duplex?

(Last modified: 17Feb2003)

This document (10023448) is provided subject to the disclaimer at the end of this document.

goal

fact

Novell NetWare 4.11

Novell NetWare 5.0

symptom

Communication problems

fix

1) Most important: There is no universal recommendation as whether to use full or half duplex. It depends entirely on the hardware you have.

2) The most important thing about half/full duplex setting of the NIC must match the half/full duplexing of the switch port to which the NIC is connected. A mismatch between the duplex settings will lead to undetected collisions which causes packet loss leading to poor performance or even loss of communication.

3) NCP over IP is *much* more sensitive to packet loss than NCP over IPX. So if you experience a severe performance degradation by going from IPX to IP, this is probably due to a half/full duplex mismatch somewhere in your net.

4) Hubs only support half duplex. Only switches can potentially support full duplex, but not all switches do.

5) Automatic negotiation (NWAYS) only works if both the NIC and the switch support NWAYS, and if both the NIC and the switch are set to automatic. If one of the two does not support NWAYS or if one of the two is statically configured to half or full duplex, the other end will not be able to determine whether the link is operating at half or full duplex speed, and it will default to half duplex.

6) The half/full duplex configuration of the server and the workstation does not have to match. For example the server can communicate full duplex with a switch while the workstation uses half duplex.

NOTE: For specific information on how to configure your LAN card for full or half duplex, contact the LAN card manufacturer.

document

Document Title:	Should I use Half Duplex or Full duplex?
Document ID:	10023448
Solution ID:	1.0.42931141.2444620
Creation Date:	16Dec1999
Modified Date:	17Feb2003
Novell Product Class:	Connectivity Products End of Life Groupware NetWare

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