Every one of us has faced the situation of troubleshooting for nearly two hours and to realize that the cable is just unplugged. A good practice when you deal with a network issue is to start from the bottom of the OSI model – the physical layer and to proceed upwards. It will save you long hours of crashing your head into the wall.

Here comes in help one really useful tool, which you can have in mind when checking the state of the link, network drivers and hardware settings:

ethtool

Pretty simple to use, the only thing you need is the devname of the network device. You can check it with:

ipconfig

The output must be something similar to:

1: lo: mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: mtu 1500 qdisc mq state UP group default qlen 1000
link/ether yy:yy:yy:yy:yy:yy brd ff:ff:ff:ff:ff:ff
inet xx.xx.xx.xx/24 brd xx.xx.xx.xx scope global dynamic eth0

Once you know the network device, we can proceed with the ethtool command itself:

sudo ethtool eth0

The information that ethtool provide us with:

root@cloudbalkan:~$ sudo ethtool eth0
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supported pause frame use: No
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Advertised pause frame use: No
Advertised auto-negotiation: Yes
Speed: 1000Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
MDI-X: on (auto)
Supports Wake-on: pumbg
Wake-on: g
Current message level: 0x00000007 (7)
drv probe link
Link detected: yes

Great – from the output above now we know that the port is up and running on 1000Mb/s and the auto-negotiation is on.

In case the cable is unplugged in the bottom of the output you will see “Link detected: No”.

If you don’t want to spend your time fighting with tangled cables and faulty NICs, start your Cloud Server now with CloudBalkan.