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IP essentials

Published 02 Jan 2021 | 1 minute read | 401 views | Linux

In later releases of the Linux OS, ip has replaced the older ifconfig to configure network interfaces. In this article we'll provide essential examples using both these commands.

Add IP address

Using 'ifconfig':

ifconfig <interface> <ip-address> netmask <netmask-addr>

Using 'ip':

ip addr add <ip-address>/<netmask> dev <interface>

For example to add address 10.10.10.10 with netmask 24 to device eth0

linux@host% sudo ifconfig eth0 10.10.10.10 netmask 255.255.255.0
linux@host% sudo ip addr add 10.10.10.10/24 dev eth0

Remove IP address

Using 'ifconfig':

ifconfig <interface> <ip-address> 0.0.0.0

Using 'ip':

ip addr del <ip-address>/<netmask> dev <interface>

For example:

linux@host% sudo ifconfig eth0 0.0.0.0
linux@host% sudo ip addr del 10.10.10.10/24 dev eth0

Down an interface

Using 'ifconfig':
```
ifconfig <interface> down
```
Using 'ip':
```
ip link set <interface> down
```

For example:

linux@host% sudo ifconfig eth0 down
linux@host% sudo ip link set eth0 down

Up an interface

Using 'ifconfig':
```
ifconfig <interface> up
```
Using 'ip':
```
ip link set <interface> up
```

For example:

linux@host% sudo ifconfig eth0 up
linux@host% sudo ip link set eth0 up

Enable Promiscious mode

Promiscuous mode is a network setting that lets a network interface card (NIC) capture and process all data packets on a network segment, not just those addressed to it, effectively allowing a device to "listen" to all traffic passing by.

Using 'ifconfig':
```
ifconfig <interface> promisc
```
Using 'ip':
```
ip link set <interface> promisc on
```

For example:

linux@host% sudo ifconfig eth0 promisc
linux@host% sudo ip link set eth0 promisc on

Show device

Using 'ifconfig':
```
ifconfig <interface>
```
Using 'ip':
```
ip addr show dev <interface>
```

For example:

linux@host% ifconfig eth0
linux@host% ip addr show dev eth0