Bring up network interface with an IP address using “ip” command

Lately many linux distributions do not ship by default with

ifconfig

which is considered as old style of setting the network when we need to do it manually.
The command is simple and self-explanatory but there is a catch! Just adding the IP won’t help you to bring up the network interface of your server. In fact we need two commands to instruct the network interface to bring up with an IP and then a third command to add a default gateway.
So here are the steps and commands to bring up an interface, set IP and gateway:

STEP 1) Add the IP to the network interface with

ip addr add 192.168.0.100/24 dev eth0

Change the IP with your IP address.

STEP 2) Bring up the interface link

ip link set eth0 up

If you omit this step a network interface, which is down won’t start and the next command (in step 3) will output an error! If your interface has been up already and you just add an additional IP to it you can skip this step (and probably the one below with the default gateway, but we do not describe this case here).

STEP 3) Bring up the interface link

ip route add default via 192.168.0.1

* The all three in one place for the right way of bringing up a network interface under linux with “ip” command:

ip addr add 192.168.0.100/24 dev eth0
ip link set eth0 up
ip route add default via 192.168.0.1

* Troubleshooting

as it was said: just adding an IP to a network interface, which is in down state, would not help to set an IP, but you would not understand it and when you tried to add the default route your would see not so informative error:

srv@local ~# ip addr add 192.168.0.100/24 dev eth0
srv@local ~# ip route add default via 192.168.0.1
ip: RTNETLINK answers: Network is unreachable

Network unreachable, but why I just added an IP. It is not enough just to add the IP, the link must also be set up, it’s like the

ifconfig eth0 up

.

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