First you need to find out the device name of your ethernet card.

You can determine the legal values for the media speed of the card by running the following command

labserver:/ # lsattr -R -l ent0 -a media_speed

Example:

labserver: # lsattr -R -l ent0 -a media_speed
10_Half_Duplex
10_Full_Duplex
100_Half_Duplex
100_Full_Duplex
1000_Full_Duplex
Auto_Negotiation
labserver: #
These are the media speeds the card will understand. To see the cards current media speed setting you can run

labserver:/ # lsattr -EH -l ent0 -a media_speed

Example 1:

labserver:/ # lsattr -EH -l ent0 -a media_speed
attribute value description user_settable

media_speed Auto_Negotiation Media speed True
labserver: #
To change the media speed, run:

labserver:/ # chdev -P -l ent0 -a media_speed=1000_Full_Duplex

The value for media_speed can be any of the values listed by the lsattr -R command above. The change does not take effect until you reboot the machine.

If you select a value other than Auto_Negotiation the switch port the machine is connected to must have the same configuration. If the switch and the machine do not match you may get no network connectivity or poor performance.

Example 2:

If you wish change the media speed without reboot, then follow below steps:

Bring down the ethernet ent0
labserver:/ # chdev -l en0 -a state=down

Remove or Detach the ethernet ent0
labserver:/ # chdev -l en0 -a state=detach

To change the media speed, run:
labserver:/ # chdev -l ent0 -a media_speed=1000_Full_Duplex

Bring up the ethernet ent0
labserver:/ # chdev -l en0 -a state=up