The other day I was having problems auto negotiating duplex settings between a remote switch and my workstation. Initially, the ndd command was used to set up the 100Mb interface in full duplex mode. But later, the /etc/system file was modified to make the settings permanent following a reboot.
Determine status
# netstat -k hme0 | grep link
# ndd -set /dev/hme adv_autoneg_cap 0
# ndd -set /dev/hme adv_100hdx_cap 0
# ndd -set /dev/hme adv_100fdx_cap 1
# vi /etc/system
#set hme:hme_adv_autoneg_cap=0
#set hme:hme_adv_100hdx_cap=0
#set hme:hme_adv_100fdx_cap=1
:wq!