Installing and Configuring 10/100Base-TX/9000
Compatibility and Installation Requirements
Manual Speed and Duplex ModeConfigurationBecause the HP-PB 10/100Base-TX/9000 card supports autonegotiation, you should not normally need to manually set the duplex mode. Sometimes you may need to manually set the duplex mode of the card--for example, if the switch is operating at full duplex but does not autonegotiate. Because the card defaults to half-duplex when autonegotiation is turned off, this could cause a mismatch between the card and switch (at either 10 or100 Mbits/s). To fix this, use the lanadmin -Xcommand as described later in this section.
The CSMA/CD media access method used in IEEE 802.3u-1995 is inherently a half-duplex mechanism. That is, at any one time, there can be only one sender of data on the link segment. It is not possible for devices on either end of the link segment to transmit simultaneously.
Since Category 5 UTP contains multiple pairs of wires, it is possible to have devices on both ends of a link segment sending data to each other simultaneously. This is known as full-duplex operation. While the details of full-duplex operation are not currently defined by IEEE 802.3u-1995 (full-duplex mode essentially involves “turning off” the CSMA/CD access method which is the foundation of IEEE 802.3), the autonegotiation mechanism defined in IEEE 802.3u-1995 allows devices to advertise and configure themselves to operate in a full-duplex mode which is essentially vendor-specific. Devices that do not support autonegotiation can sometimes be manually configured to operate in full-duplex mode.
Full-duplex mode is most commonly found in, and indeed only makes sense for, switches rather than hubs. It may be found in either 10 Mbit/s or 100 Mbit/s switch devices. Full-duplex mode may provide a throughput advantage under some circumstances, the degree of the advantage is application-dependent.
The HP-PB 10/100Base-TX card supports both half and full-duplex operation.
Ensure that the speed, duplex mode, and autonegotiation of the associated switch are configure the same as on the HP-PB 10/100Base-TX card. If the switch supports autonegotiation on the ports connected to the cards, this should be enabled as explained in the section in this release note called “Autonegotiation and Autosensing.”