The ndd command is also used to check for link mode, link status, and link speed of an Ethernet interface. Here's an example.
# ifconfig -a
lo0: flags=1000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv4> mtu 8232 index 1
inet 127.0.0.1 netmask ff000000
hme0: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 2
inet 192.xxx.xx.xx netmask ffffff00 broadcast 192.xxx.xx.xxx
ether 8:0:20:xx:xx:xx
# ndd -set /dev/hme instance 0
# ndd -get /dev/hme link_mode
1
# ndd -get /dev/hme link_status
1
# ndd -get /dev/hme link_speed
1
What do the return values mean?
mode: 0 is half duplex and 1 is full duplex
status: 0 is down and 1 is up
speed: 0 is 10 megabits and 1 is 100 megabits