Link Speeds
ethtool
see ethtool
Powershell
Get-NetAdapter|select name, status, linkspeed, MacAddress
WMIC
wmic nic where netEnabled=true get name,speed
IT Notes from various projects because I forget, and hopefully they help you too.
see ethtool
Get-NetAdapter|select name, status, linkspeed, MacAddress
wmic nic where netEnabled=true get name,speed