Changing the media speed settings of your p570/p520 nic.

Bring the interface down

ifconfig en0 down;

Detach the driver

ifconfig en0 detach;

Change charecs of the interface

chdev -l 'ent0' -a media_speed='100_Full_Duplex'

Using Smitty : do the following ->

smitty chdev
-> Communication
Then adapter - etc and change 'media speed' by selecting with F4

ifconfig en0 attach;

ifconfig en0 up;