Manual Speed and Duplex Mode Configuration

Because this PCI 10/100Base-TX/9000 LAN 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 -X command 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, but the degree of the advantage is application-dependent.

The PCI 10/100Base-TX card supports both half- and full-duplex operation.

Ensure that the speed, duplex mode, and autonegotiation of the associated switch are configured the same as on the PCI 10/100Base-TX card. If the switch supports autonegotiation on the ports connected to the cards, this should be enabled as explained in “Autonegotiation and Autosensing”.

To manually set the duplex mode of the PCI card, first ensure that your computer has the latest applicable patches installed as listed in the Required and Optional Patches section of this release note.

To list the current speed and duplex mode of the PCI 10/100Base-TX/9000 card, use the -x option (NOTE: lowercase x) of the lanadmin command. Determine the speed and duplex mode of your hub or switch before performing manual configuration as follows:

lanadmin -x ppa (HP-UX 10.30 or 11.0)

lanadmin -x nmid (HP-UX 10.20)

To manually set the duplex mode of the interface, install one of the patches above and then use the -X option of lanadmin as follows:

lanadmin -X mode ppa (on HP-UX 10.30 and 11.0)

lanadmin -X mode nmid (on HP-UX 10.20)

where:

mode can be any one of the following strings (and the fd or hd are case-insensitive):

10fd =10 full-duplex

10hd =10 half-duplex

100fd =100 full-duplex

100hd =100 half-duplex

and

lanadmin -X auto_on ppa (turns autonegotiation on for HP-UX 10.30 and 11.0)

lanadmin -X auto_on nmid (turns autonegotiation on for HP-UX 10.20)

The ppa is the physical point of attachment on HP-UX 10.30 or 11.0. On HP-UX 10.20, use the nmid or Network Management ID of the card. You can get the ppa (nmid) from the output of the lanscan command.

Example:

If the ppa (nmid on HP-UX 10.20) of the 100Base-TX interface is 5, the command to set the card to 10Mbits/s and full-duplex mode would be:

lanadmin -X 10fd 5

After issuing the lanadmin -X, you must wait at least 11 seconds before attempting to use the specified network interface.

If you want the Duplex Mode setting to be effective in all subsequent reboots, you must enter the information in the following file:

/etc/rc.config.d/hpbtlanconf

Manually configuring the speed or duplex setting of a switch port on some switches may disable that switch port from doing autonegotiation. Verify that both the card and the switch port are operating in the same speed and duplex mode as desired.

If you use manual configuration to change the card to a different speed and duplex mode, you may need to turn autonegotiation on first before the manual setting takes place.

	NOTE: Mismatches between the speed, autonegotiation, or duplex mode of the card and switch will cause incorrect operation.