How To Use Ip Command.

This article explains how to use the ip command through practical examples and detailed explanations of the most common options.

The ip command is a powerful tool for configuring network interfaces that any Linux system administrator should know. It is used to bring interfaces up or down, assign and remove addresses and routes, manage ARP cache, and much more.

How to Use the ip Command

The ip utility is a part of the iproute2 package that is installed on all modern Linux distributions.

The syntax for the ip command is as follows:

ip [ OPTIONS ] OBJECT { COMMAND | help }

OBJECT is the object type that you want to manage. The most frequently used objects (or subcommands) are:

• link (l) – Display and modify network interfaces.

• address (a) – Display and modify IP Addresses.

• route (r) – Display and alter the routing table.

• neigh (n) – Display and manipulate neighbor objects (ARP table).

The object can be written in full or abbreviated (short) form. To display a list of commands and arguments for each object, enter, ip OBJECT help.

When configuring network interfaces, you must execute the commands as root or user with sudo privileges. Otherwise, the command will print RTNETLINK answers: Operation not permitted.

The configurations set with the ip command are not persistent. After a system restart, all changes are lost. To make the changes permanent, you need to edit the distro-specific configuration files or add the commands to a startup script.

Displaying and Modifying IP Addresses

When operating with the addr object the commands take the following form:

ip addr [ COMMAND ] ADDRESS dev IFNAME

The most frequently used COMMANDS of the addr object are: show, add, and del.

Display information about all IP addresses

To display a list of all network interfaces and the associated ip address type the following command:

ip addr show

The output will look something like this:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    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: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:16:3e:39:e7:1f brd ff:ff:ff:ff:ff:ff
    inet 5.254.113.196/26 brd 5.254.113.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::216:3eff:fe39:e71f/64 scope link
       valid_lft forever preferred_lft forever

You will get the same output if you type omit the show command and type: ip addr.

If you want to display only IPv4 or IPv6 ip addresses, use ip -4 addr or ip -6 addr.

Display information about a single network interface

To get information about a specific network interface, use ip addr show dev followed by the device name. For example, to query eth0, you would type:

ip addr show dev eth0

Assign IP addresses to an interface

To assign an IP address to an interface, use the following syntax:

ip addr add ADDRESS dev IFNAME

Where IFNAME is the interface name and ADDRESS is the IP address you want to assign to the interface.

To add address 192.168.121.45 with netmask 24 to device eth0, you would type:

sudo ip address add 5.254.113.196/26 dev eth0

On success, the command will not show any output. If the interface doesn’t exist, you will get Cannot find device “eth0”.

Assign multiple IP addresses to the same interface

With ip, you can assign multiple addresses to the same interface. For example:

sudo ip address add 169.254.0.0/16 dev eth0sudo ip address add 5.254.113.196/26 dev eth0

To confirm the IPs are assigned type ip -4 addr show dev eth0 or ip -4 a show dev eth0:

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    inet 169.254.0.0/16 brd 192.168.121.255 scope global dynamic eth0
       valid_lft 3515sec preferred_lft 3515sec
    inet 5.254.113.196/26 scope global secondary eth0
       valid_lft forever preferred_lft forever

Remove / Delete an IP address from the interface

The syntax to remove an IP address from an interface is as below:

ip addr dev ADDRESS dev IFNAME

IFNAME is the interface name, and ADDRESS is the IP address you want to remove from the interface.

To remove address 5.254.113.196/26 from device eth0 type:

sudo ip address del 5.254.113.196/26 dev eth0

Displaying and Modifying Network Interfaces

To manage and view the state of the network interfaces, use the link object.

When working with the link objects, the most commonly used commands are: show, set, add, and del.

Display information about network interfaces

To display a list of all network interfaces, type the following command:

ip link show

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
    link/ether 00:16:3e:39:e7:1f brd ff:ff:ff:ff:ff:ff

Unlike ip addr show, ip link show will not print information about the IP addresses associated with the device.

To get information about a specific network interface, use ip link show dev followed by the device name. For example, to query eth0 you would type:

ip link show dev eth0

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
    link/ether 00:16:3e:39:e7:1f brd ff:ff:ff:ff:ff:ff

Alter the status of the interface UP/DOWN

To bring interfaces up or down, use the ip link set dev followed by the device name and the desired state:

ip link set dev {DEVICE} {up|down}

For example, to bring the interface eth0 online, you would type:

ip link set eth0 up

And to bring if offline

ip link set eth0 down

Displaying and Altering the Routing Table

To assign, remove, and display the kernel routing table use the route object. The most commonly used commands when working with the routes objects are: list, add, and del.

Display routing table

To get a list of the kernel route entries, use one of the following commands:

ip route
ip route list
ip route list SELECTOR

When used without a SELECTOR the command will list all of the route entries in the kernel:

ip route list

5.254.113.192/26 dev eth0 proto kernel scope link src 5.254.113.196
169.254.0.0/16 dev eth0 scope link metric 1002

Add a new route

To add a new entry to the routing table, use the route add command followed by network or device name.

Add a route to 192.168.121.0/24 via the gateway at 192.168.121.1

ip route add 192.168.121.0/24 via 192.168.121.1

Add a route to 192.168.121.0/24 that can be reached on device eth0.

ip route add 192.168.121.0/24 dev eth0

To add a default route, use the keyword default. The following command will add a default route via the local gateway 192.168.121.1 that can be reached on device eth0.

ip route add default via 192.168.121.1 dev eth0

Delete a route

To delete an entry from the routing table, use the route add command. The syntax for deleting a route is the same as when adding.

The following command will delete the default route:

ip route del default

Delete a route for 192.168.121.0/24 via the gateway at 192.168.121.1

ip route add 192.168.121.0/24 via 192.168.121.1

Conclusion

By now, you should have a good understanding of how to use the Linux ip command. For more information about the other ip options, visit the ip command man page or type man ip in your terminal.