Linux ip Command with Examples

By 

Dejan Panovski
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Updated on

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14 min read

Linux ip Command

When a server comes back from a reboot without network access, the first thing to check is which interfaces are up and which addresses they have. On modern Linux systems, you do that with the ip command. It is used to bring interfaces up or down, assign and remove addresses and routes, manage ARP cache, and much more.

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

Planning an IP scheme? Our interactive subnet calculator breaks any CIDR block into its network, broadcast, and usable host range.

How to Use the ip Command

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

The syntax for the ip command is as follows:

txt
ip [OPTIONS] OBJECT { COMMAND | help }

OBJECT is the object type you want to manage. The most frequently used objects 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).

Each object can be written in full or abbreviated form. To display a list of commands and arguments for a given object, run ip OBJECT help.

OPTIONS change how the output looks or which address family is shown. The ones you will use most often are:

  • -4 - Show only IPv4 information.
  • -6 - Show only IPv6 information.
  • -br - Print a brief, one-line summary per interface.
  • -c - Color the output.
  • -s - Show statistics. Repeat it (-s -s) for more detail.
  • -d - Show detailed information, such as the link type.
  • -j - Print the output in JSON format.

When configuring network interfaces, you must run the commands as root or a 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 changes permanent, you need to edit the distribution-specific network configuration files or add the commands to a startup script.

Displaying and Modifying IP Addresses

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

txt
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 their associated IP addresses:

Terminal
ip addr show
output
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 noprefixroute
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 52:54:00:8c:62:44 brd ff:ff:ff:ff:ff:ff
    inet 192.168.121.241/24 brd 192.168.121.255 scope global dynamic eth0
       valid_lft 2900sec preferred_lft 2900sec
    inet6 fe80::5054:ff:fe8c:6244/64 scope link proto kernel_ll
       valid_lft forever preferred_lft forever

Each interface block starts with the index number and the interface name, followed by the flags in angle brackets. UP means the interface is enabled, and LOWER_UP means the physical link is up. The state field shows the operational state, and mtu is the largest packet size the interface can send.

The link/ether line shows the MAC address of the interface. Each inet line is an IPv4 address with its prefix length, and each inet6 line is an IPv6 address. The dynamic keyword marks a nonpermanent address. In this example, the IPv4 address was assigned by DHCP, but IPv6 addresses configured through router advertisements can also be dynamic. valid_lft shows how long the address remains valid, in seconds or as forever.

You will get the same output if you omit show and type ip addr, or use the shortest form, ip a. To display only IPv4 or IPv6 addresses, use ip -4 addr or ip -6 addr.

Display Addresses in Brief Format

On systems with several interfaces, the full output gets long. The -br option prints one line per interface with its name, state, and addresses:

Terminal
ip -br a
output
lo               UNKNOWN        127.0.0.1/8 ::1/128
eth0             UP             192.168.121.241/24 fe80::5054:ff:fe8c:6244/64

The first column is the interface name, the second is the operational state, and the rest of the line lists the assigned addresses. The loopback interface always reports UNKNOWN, so you can ignore that state.

The same option works with the link object. Instead of addresses, ip -br link prints the MAC address and the interface flags:

Terminal
ip -br link
output
lo               UNKNOWN        00:00:00:00:00:00 <LOOPBACK,UP,LOWER_UP>
eth0             UP             52:54:00:8c:62:44 <BROADCAST,MULTICAST,UP,LOWER_UP>

To make the output easier to scan in a terminal, add the -c option. Interface names, states, and addresses are printed in different colors:

Terminal
ip -c -br a

If you need the data in a script, use -j to get JSON output:

Terminal
ip -j -br a show lo
output
[{"ifname":"lo","operstate":"UNKNOWN","addr_info":[{"local":"127.0.0.1","prefixlen":8},{"local":"::1","prefixlen":128}]}]

Display Information about a Single Interface

To get information about a specific network interface, use ip addr show dev followed by the device name:

Terminal
ip addr show dev eth0

Assign an IP Address to an Interface

To assign an IP address to an interface:

txt
ip addr add ADDRESS dev IFNAME

Where IFNAME is the interface name and ADDRESS is the IP address with its prefix length.

To add address 192.168.121.45/24 to device eth0:

Terminal
sudo ip address add 192.168.121.45/24 dev eth0

On success, the command produces no output. If the interface does not exist, you will get Cannot find device "eth0". If the address is already set on the interface, the command fails with Error: ipv4: Address already assigned.

Assign Multiple IP Addresses to the Same Interface

With ip, you can assign multiple addresses to the same interface. To add two more addresses to eth0:

Terminal
sudo ip address add 192.168.121.46/24 dev eth0
sudo ip address add 192.168.121.47/24 dev eth0

To confirm the IPs are assigned:

Terminal
ip -4 addr show dev eth0
output
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    inet 192.168.121.241/24 brd 192.168.121.255 scope global dynamic eth0
       valid_lft 3515sec preferred_lft 3515sec
    inet 192.168.121.45/24 scope global secondary eth0
       valid_lft forever preferred_lft forever
    inet 192.168.121.46/24 scope global secondary eth0
       valid_lft forever preferred_lft forever
    inet 192.168.121.47/24 scope global secondary eth0
       valid_lft forever preferred_lft forever

The first address in a subnet is the primary one. Every address you add later in the same subnet is marked as secondary.

Remove an IP Address from an Interface

To remove an IP address from an interface:

txt
ip addr del ADDRESS dev IFNAME

To remove address 192.168.121.45/24 from device eth0:

Terminal
sudo ip address del 192.168.121.45/24 dev eth0
Warning
ip addr flush also removes the address you are connected through. Do not run it on the interface that carries your SSH session unless you have console access to the machine.

To remove all IP addresses from an interface at once, use flush:

Terminal
sudo ip addr flush dev eth0

Displaying and Modifying Network Interfaces

To manage and view the state of network interfaces, use the link object. The most commonly used commands are show, set, add, and del.

Display Information about Network Interfaces

To display a list of all network interfaces:

Terminal
ip link show
output
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 fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:8c:62:44 brd ff:ff:ff:ff:ff:ff

Unlike ip addr show, ip link show does not print IP address information.

To query a specific interface:

Terminal
ip link show dev eth0
output
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:8c:62:44 brd ff:ff:ff:ff:ff:ff

Bring an Interface Up or Down

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

txt
ip link set dev DEVICE { up | down }

To bring eth0 online:

Terminal
sudo ip link set eth0 up
Warning
If you are connected to the machine over SSH, bringing down the interface that carries your session disconnects you. You will need console access to bring it back up.

To bring it offline:

Terminal
sudo ip link set eth0 down

Change the MTU of an Interface

The set command also changes link settings such as the MTU. To set the MTU of eth0 to 9000 bytes:

Terminal
sudo ip link set dev eth0 mtu 9000

Larger MTU values (jumbo frames) work only when the network card, the switch, and the other host all support them. Otherwise, large packets are dropped.

Display Interface Statistics

To view packet and error statistics for an interface, use the -s flag:

Terminal
ip -s link show dev eth0
output
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:8c:62:44 brd ff:ff:ff:ff:ff:ff
    RX:  bytes packets errors dropped  missed   mcast
    1923498    8438      0       0       0     204
    TX:  bytes packets errors dropped carrier collsns
     842103    5565      0       0       0       0

The RX lines show received traffic, and the TX lines show transmitted traffic. If the errors or dropped counters keep growing, investigate further. Errors can indicate problems with the cable, driver, or network card, while drops can also result from resource shortages or unsupported protocols. These counters alone do not identify the cause.

Displaying and Altering the Routing Table

To assign, remove, and display kernel routing table entries, use the route object.

Display the Routing Table

To list all kernel route entries:

Terminal
ip route list
output
default via 192.168.121.1 dev eth0 proto dhcp src 192.168.121.241 metric 100
192.168.121.0/24 dev eth0 proto kernel scope link src 192.168.121.241
192.168.121.1 dev eth0 proto dhcp scope link src 192.168.121.241 metric 100

The first line is the default route. Traffic for any destination without a more specific route goes to the gateway 192.168.121.1 through eth0.

The proto field shows who added the route. proto dhcp means the route came from the DHCP client, and proto kernel means the kernel created it when the address was assigned. src is the source address for outgoing packets, and metric is the route priority. Within a routing table, the kernel first chooses the longest matching destination prefix. When routes have the same destination prefix, the one with the lower metric is preferred.

To display routing for a specific network:

Terminal
ip route list 172.17.0.0/16
output
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 linkdown

Find Which Route a Packet Takes

To see which route the kernel uses for a specific destination, use ip route get:

Terminal
ip route get 1.1.1.1
output
1.1.1.1 via 192.168.121.1 dev eth0 src 192.168.121.241 uid 1000
    cache

The output shows the gateway, the outgoing interface, and the source address the kernel would use for that destination. This is useful on hosts with several interfaces or a VPN connection. On those systems, it is not always obvious which path a connection takes.

Add a New Route

To add a route to the 10.10.0.0/24 network via the gateway at 192.168.121.1:

Terminal
sudo ip route add 10.10.0.0/24 via 192.168.121.1

To add a route to a network that is reachable directly on device eth0:

Terminal
sudo ip route add 10.20.0.0/24 dev eth0

To add a default route via the gateway 192.168.121.1 on device eth0:

Terminal
sudo 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 del command with the same syntax as route add.

To delete a specific route:

Terminal
sudo ip route del 10.10.0.0/24 via 192.168.121.1
Warning
Deleting the default route leaves directly connected networks and destinations covered by other routes reachable. Traffic to destinations without a matching route cannot be sent. If your SSH session depends on the default route, deleting it disconnects you.

To delete the default route:

Terminal
sudo ip route del default

Displaying and Manipulating the ARP Table

The neigh object manages the neighbor (ARP) table, which maps IP addresses to MAC addresses on the local network.

To display the current ARP table:

Terminal
ip neigh show
output
192.168.121.1 dev eth0 lladdr 52:54:00:12:35:02 REACHABLE
192.168.121.10 dev eth0 lladdr 52:54:00:9a:41:af STALE

Each line shows the neighbor IP address, the interface, and the MAC address after lladdr. REACHABLE means the entry was confirmed recently. STALE means the entry has not been used for a while, and the kernel checks it again the next time it sends traffic to that address.

To add a static ARP entry:

Terminal
sudo ip neigh add 192.168.121.50 lladdr 00:11:22:33:44:55 dev eth0

Static entries do not expire and are shown with the PERMANENT state.

To delete an ARP entry:

Terminal
sudo ip neigh del 192.168.121.50 dev eth0

To flush dynamic ARP entries for an interface:

Terminal
sudo ip neigh flush dev eth0

By default, flush leaves entries in the PERMANENT and NOARP states intact.

Quick Reference

For a printable quick reference, see the IP command cheatsheet .

CommandDescription
ip aShow all IP addresses
ip -br aShow a one-line summary per interface
ip addr show dev eth0Show addresses for one interface
ip addr add IP/PREFIX dev eth0Assign an IP address
ip addr del IP/PREFIX dev eth0Remove an IP address
ip addr flush dev eth0Remove all addresses from an interface
ip link showShow all interfaces
ip link set eth0 upBring interface up
ip link set eth0 downBring interface down
ip link set dev eth0 mtu 9000Change the MTU
ip -s link show dev eth0Show interface statistics
ip route listShow routing table
ip route get IPShow the route used for a destination
ip route add default via GW dev eth0Add default route
ip route del defaultDelete default route
ip neigh showShow ARP table
ip neigh flush dev eth0Flush ARP entries for interface

Troubleshooting

“RTNETLINK answers: Operation not permitted”
The command requires root privileges. Prefix it with sudo: sudo ip link set eth0 up.

“Cannot find device”
The interface name is wrong or the interface does not exist. List available interfaces with ip -br link to find the correct name. Modern systems use names like ens3, enp0s1, or wlp2s0 instead of eth0.

“Error: ipv4: Address already assigned.”
The address is already set on that interface. Check the current addresses with ip -br a. To change the prefix length, delete the address first with ip addr del, then add it again.

ip route add fails with “RTNETLINK answers: File exists”
A route for the same destination already exists. Delete the existing route first with ip route del DESTINATION, then re-add it.

Changes lost after reboot
The ip command applies changes only to the running kernel state. To make them persistent, add the configuration to your distribution’s network configuration: Netplan on Ubuntu, NetworkManager with nmcli , systemd-networkd, or /etc/network/interfaces on Debian.

FAQ

What does ip a do?
ip a is the short form of ip address show. It lists every network interface with its IPv4 and IPv6 addresses. The ip command accepts abbreviated object names, so ip a, ip addr, and ip address all run the same command.

What is the difference between ip and ifconfig?
ifconfig is part of the older net-tools package and is deprecated on most modern Linux distributions. ip from the iproute2 package is the replacement. It supports more features, has a consistent syntax across all network objects, and is actively maintained.

How do I make ip changes persistent across reboots?
The ip command modifies the running kernel state only. To persist changes, configure your network manager: systemd-networkd (edit files in /etc/systemd/network/), NetworkManager (use nmcli or connection files), or the distro-specific interface configuration.

How do I find my server’s IP address?
Run ip addr show and look for inet lines. The loopback address 127.0.0.1 is the local machine; any other inet address on an active interface is your network IP. For other methods, including how to find your public IP, see How to Find Your IP Address in Linux .

What does the /24 mean in an IP address like 192.168.1.1/24?
The /24 is the prefix length (CIDR notation). It defines the subnet mask: /24 means the first 24 bits are the network portion, equivalent to a 255.255.255.0 netmask. This tells the system which addresses are on the local network. For prefix-to-mask conversion and subnet math, see CIDR Notation and Subnetting Explained .

Can I use ip to monitor network traffic?
The ip -s link show command shows basic packet and error counters. For detailed traffic monitoring, use dedicated tools like ss , netstat , iftop, or tcpdump .

Conclusion

The ip command replaces the older ifconfig and route commands on modern Linux systems and manages addresses, interfaces, routes, and the ARP table with one consistent syntax. For more details on available options, run man ip or ip OBJECT help.

Tags

networking linux commands

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About the authors

Dejan Panovski

Dejan Panovski

Dejan Panovski is the founder of Linuxize, an RHCSA-certified Linux system administrator and DevOps engineer based in Skopje, Macedonia. Author of 1000+ Linux tutorials with 20+ years of experience turning complex Linux tasks into clear, reliable guides.

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