Here are some commands to help troubleshoot network card issues on Ubuntu:
Determine Speed and Duplex
dmesg |grep eth0
Most useful
Command:
sudo lshw -c network
Displays details of all network adapters in your system including the identity used for configuring the adapter (e.g. eth0, enp2s0, etc.)
*-network
description: Ethernet interface
product: 82572EI Gigabit Ethernet Controller (Copper)
vendor: Intel Corporation
physical id: 0
bus info: pci@0000:04:00.0
logical name: enp2s0
version: 06
serial: 00:0A:0A:0A:0A:0A
size: 1Gbit/s
capacity: 1Gbit/s
width: 32 bits
clock: 33MHz
capabilities: pm msi pciexpress bus_master cap_list rom ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
configuration: autonegotiation=on broadcast=yes driver=e1000e driverversion=3.2.6-k duplex=full firmware=5.11-10 latency=0 link=yes multicast=yes port=twisted pair speed=1Gbit/s
resources: irq:01 memory:00000000-ffffffff memory:00000000-ffffffff ioport:dc00(size=32) memory:00000000-ffffffff
Less useful
Command:
sudo ip addr
This command will display output from your network adapters.
2: enp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0A:0A:0A:0A:0A brd ff:ff:ff:ff:ff:ff
inet 192.168.1.5/24 brd 192.168.1.255 scope global enp5s2
valid_lft forever preferred_lft forever
inet6 fe80::000:0000:0000:0000/64 scope link
valid_lft forever preferred_lft forever
Command:
sudo ip addr flush dev eth0
For those times when a network adapter's configuration may be cached and you need to clear it in order to use ifup
Command
lspci | egrep -i --color 'network|ethernet'
Displays details about the network adapters in your system
04:00.0 Ethernet controller: Intel Corporation 82572EI Gigabit Ethernet Controller (Copper) (rev 06)