When you finish installing Ubuntu , you see that there is no network card when running "ifconfig" , or checking /etc/network/interfaces , but you see there is no info for your network card.
lspci -nn | grep -i net
The following command will show a list of ethernet card available in your Ubuntu box.
The output may look like this
09:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5761e Gigabit Ethernet PCIe (rev 10)
If you see the result, that means the network card has been recognized by your OS , then you just need to configure it
you can add these line to bring that interface up
auto eth0
iface eth0 inet static
address 192.168.1.100
netmask 255.255.255.0
network 192.168.1.0
Then run this :
ifup eth1
There is another tool to check the network card speed …
ethtool eth0