How to Use the Linux IP Command

The Linux ip command is a system tool for network administration, but it has many options and can be complicated. Fortunately, most users find the tool easier to use when they understand its main components. This guide explains how to configure a server using the ip command. It demonstrates how to accomplish common networking tasks and how to view the state of the network.

As its name suggests, the ip command relates to the Internet Protocol (IP). IP Version 4 (Ipv4) and version 6 (Ipv6) jointly define the framework of the modern internet. The IP protocol describes the addressing system used to identify network interfaces and send and receive traffic.

Hosts and routers use the IP system to direct traffic across the internet to the correct destination. Each network interface on a system has a media access control (MAC) address and can be assigned one or more IPv4 or Ipv6 addresses. In addition, each server maintains a routing table. The routing table determines which interface to use when transmitting a packet to a given destination IP address.

The Linux ip command lets administrators view the system’s IP networking information from the command line. It permits them to configure network interfaces, routing information, and Ipv4/Ipv6 addresses. The ip command also includes advanced capabilities to set up IP tunneling, route policies, and configure Address Resolution Protocol (ARP) information for the system’s neighbors.

The ip command is part of the Linux iproute2 collection of networking utilities. It replaces the old ifconfig command, which had more limited functionality and fewer options. The ip package is pre-installed on all modern Linux distributions, including Ubuntu.

1. If you have not already done so, create a Linode account and Compute Instance. See our Getting Started with Linode and Creating a Compute Instance guides.

2. Follow our Setting Up and Securing a Compute Instance guide to update your system. You may also wish to set the timezone, configure your hostname, create a limited user account, and harden SSH access.

Note

This guide is written for a non-root user. Commands that require elevated privileges are prefixed with sudo. If you are not familiar with the sudo command, see the Users and Groups guide.

Each of the Linux ip commands acts upon one or more ip objects. An ip object represents a specific component of the networking system, such as the routing table. Some of the ip terminology differs from the way networking concepts are more typically discussed. Here is a list of some of the most important ip objects, with the shortcuts in parentheses.

• link (l): A link represents a network device. Most links, other than the loopback link, connect the server to a wider computer network. A link can be logical/abstract or physical.
• route (r): This represents an entry in the routing table. It is used to determine how and where to send an outgoing packet based on its address.
• address (a): This is the Ipv4 or Ipv6 address associated with a link.
• maddress (m): This is the multicast address, if any, configured on a link.
• neighbor (n): This represents information about a neighboring interface. It includes cached ARP or Ipv6 Neighbor Discovery (NDISC) information.
• rule (ru): This is a policy rule for routing packets. It controls the precedence of the routes in the routing database.

Other ip objects include addrlabel, l2tp, mroute (for multicast route), tunnel, and xfrm, which is used by the Internet Protocol Security (IPsec) protocol. See the Ubuntu ip documentation for more information about the remaining ip objects.

Note

Some of the objects in the ip command do not map perfectly to the terminology used in more casual discussions about networking. For instance, the term link often refers to a connection between two systems. The link ip object is usually called an interface. To avoid confusion, use the precise names of the ip objects when discussing the ip command.

The ip command is the newer iteration of the established ifconfig command. ip also includes functionality from other commands including route and arp. Thus it has a broader scope and more features than the more limited ifconfig.

The ip utility features other enhancements. For instance, it displays all interfaces, whereas ifconfig only displays enabled interfaces. The ip command is also more efficient and interacts with the system in a more seamless manner. An ip command always requires an object type such as the address or link identifier, whereas ifconfig directly references the interface without an ip object.

The ip command can be intimidating at first due to its complexity, so some users might initially feel more comfortable using ifconfig. Users can still install ifconfig using the apt install net-tools command, but this is not recommended. Unfortunately, ifconfig might still be used by legacy utilities and applications that have not been updated recently.

The ip command is straightforward to use, but it includes many complex options. It is not possible to use the ip command by itself. One of the “ip objects” must also be included. In other words, there is no way to use the command to display all networking information at once. To configure network settings using the ip command, include the following information:

• The ip command name.
• Zero or more options.
• The name of the “ip object”, for example, link or route. Each object is associated with an abbreviation. For instance, the link object can be abbreviated as l. ip l show and ip link show both refer to the same command.
• The command, show for example, along with any parameters.

Most ip commands follow this format:

ip [options] OBJECT COMMAND

Non-root users must use sudo to execute any ip command that changes the network configuration. The show commands are available to all users.

The ip help directive describes the command syntax and lists all available options. More specific help is available for each ip object. Use the format ip OBJECT help. For example, ip addr help provides instructions for the address-related commands.

ip addr help

Usage: ip address {add|change|replace} IFADDR dev IFNAME [ LIFETIME ]
                                                      [ CONFFLAG-LIST ]
       ip address del IFADDR dev IFNAME [mngtmpaddr]
       ip address {save|flush} [ dev IFNAME ] [ scope SCOPE-ID ]
                            [ to PREFIX ] [ FLAG-LIST ] [ label LABEL ] [up]
       ip address [ show [ dev IFNAME ] [ scope SCOPE-ID ] [ master DEVICE ]
                         [ type TYPE ] [ to PREFIX ] [ FLAG-LIST ]
                         [ label LABEL ] [up] [ vrf NAME ] ]
       ip address {showdump|restore}
IFADDR := PREFIX | ADDR peer PREFIX
          [ broadcast ADDR ] [ anycast ADDR ]
          [ label IFNAME ] [ scope SCOPE-ID ] [ metric METRIC ]
...

Here are some of the more useful ip options.

• -a: Processes all objects, provided the command supports the option.
• -d: Adds extra details to the output.
• -f: Specifies the protocol family. Some common families have their own shortcuts. -4 is a shortcut for IPv4, -6 denotes IPv6, and M indicates MPLS.
• -j: Displays the output in JSON format.
• -p: Presents the output in a more readable format.
• -s: Displays extra statistics, including packets transferred and received. The -s -s option displays even more information.
• -t: Includes the timestamp in the output.

For a more thorough explanation of all ip options, see the man page for the ip command.

Because the ip command contains so many options, the following examples focus on some of the more common use cases.

Note

Changes made using the ip command are not persistent across a system reboot. To automatically configure networking information, add the information to a startup script. Each distribution also provides a method to make networking changes using its system configuration files.

Caution

Be very careful when making any changes to the network interfaces, addresses, and routes. It is easy to cut the server off from the main network, necessitating a system reboot. Consider using official test addresses and MAC addresses when trying out new commands.

The addr object allows users to list the IP addresses associated with each link, including the system address. It is also used to add, modify, and remove addresses.

Use the addr ip object to find your IP address. The ip addr show command displays the addresses for every link configured on the system. Locate the eth0 link, which connects the host to the wider network on most systems. The inet field displays the Ipv4 address. If an Ipv6 address is configured, it is indicated in the inet6 section.

ip addr show

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 mq state UP group default qlen 1000
    link/ether f2:3c:93:60:50:30 brd ff:ff:ff:ff:ff:ff
    inet 178.79.148.108/24 brd 178.79.148.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 2a01:7e00::f03c:93ff:fe60:5030/64 scope global dynamic mngtmpaddr noprefixroute
       valid_lft 5155sec preferred_lft 1555sec
    inet6 fe80::f03c:93ff:fe60:5030/64 scope link
       valid_lft forever preferred_lft forever

To display information about one particular link, append the name of the link to the end of the command.

ip addr show eth0

The -br option simplifies the display to the state and IP addresses.

ip -br addr show

lo               UNKNOWN        127.0.0.1/8 ::1/128
eth0             UP             178.79.148.108/24 2a01:7e00::f03c:93ff:fe60:5030/64 fe80::f03c:93ff:fe60:5030/64

Note

There are other methods for determining the IP address of a system. For more information on how to find the IP address of a system, see the Linode guide How to understand IP addresses.

To add an IP address to an existing link/interface, use the addr add command. The format for the command is ip addr add ADDRESS/NETMASK dev LINK_ID. Separate the IP address and the netmask using the / symbol.

The following command demonstrates how to add a new address to the lo loopback link. You must use sudo when modifying any network information. If the rule already exists, ip displays the error message RTNETLINK answers: File exists.

sudo ip addr add 127.255.255.255/16 dev lo

The addr show command reflects the new configuration change.

ip addr show dev lo

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
    inet 127.255.255.255/16 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever

To remove an address from a link, use the addr delete command.

sudo ip addr delete 127.255.255.255/16 dev lo

To configure the address as a broadcast address, use the keyword brd.

sudo ip addr add 172.31.255.255 brd + dev eth1

The link object can access and configure information about the network interfaces on the system. It is used to view the status of a network device, or set the administrative state to up or down.

To view information about all network interfaces on the server, use the ip link show command. The command shows the state, MTU, and MAC address for each link object amongst other information.

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 mq state UP mode DEFAULT group default qlen 1000
    link/ether f2:3c:93:60:50:30 brd ff:ff:ff:ff:ff:ff

When the -br option is added, ip only displays the most important information.

ip -br link show

lo               UNKNOWN        00:00:00:00:00:00 <LOOPBACK,UP,LOWER_UP>
eth0             UP             f2:3c:93:60:50:30 <BROADCAST,MULTICAST,UP,LOWER_UP>

To only show information about links that are operationally active, append the keyword up.

ip link show up

To limit the display to information about a specific interface, append the name of the information to the ip link show command. The following command only displays information about the eth0 network interface. If the interface does not exist, ip returns the error message Device "INTERFACE" does not exist.

ip link show eth0

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
    link/ether f2:3c:93:60:50:30 brd ff:ff:ff:ff:ff:ff

Add the -s option to see the link/interface statistics.

ip -s link show dev eth0

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
    link/ether f2:3c:93:60:50:30 brd ff:ff:ff:ff:ff:ff
    RX:  bytes packets errors dropped  missed   mcast
      67487882  470575      0       0       0       0
    TX:  bytes packets errors dropped carrier collsns
     112143192  522462      0       0       0       0

Use the -s -s double flag to see even more comprehensive statistics, including information about the various errors.

ip -s -s link show dev eth0

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
    link/ether f2:3c:93:60:50:30 brd ff:ff:ff:ff:ff:ff
    RX:  bytes packets errors dropped  missed   mcast
      67589398  471467      0       0       0       0
    RX errors:  length    crc   frame    fifo overrun
                     0      0       0       0       0
    TX:  bytes packets errors dropped carrier collsns
     112345201  523306      0       0       0       0
    TX errors: aborted   fifo  window heartbt transns
                     0      0       0       0       2

Modify the status of any network interface using the ip link set command. Use the keyword up to enable an interface and the keyword down to disable it.

To disable the eth1 link, use the following command.

sudo ip link set eth1 down

To bring eth1 back up, enter this command.

sudo ip link set eth1 up

Use the following command to set the maximum transmission unit (MTU) size for the link.

sudo ip link set mtu 1600 eth1

The route object allows users to view the routing tables. It is also used to add and delete a route.

To view all routes installed in the routing database, use the ip route show command.

Note

Many servers access the internet through a default gateway, resulting in relatively few routes. Even if ip route show only displays one or two routes, this does not usually indicate a problem.

ip route show

default via 178.79.148.1 dev eth0 proto static
178.79.148.0/24 dev eth0 proto kernel scope link src 178.79.148.108

It is also possible to list all routes for a particular network using the list command.

ip route list 178.79.148.0/24

178.79.148.0/24 dev eth0 proto kernel scope link src 178.79.148.108

To add a new route, use the ip route add command. There are two ways to add a route. For the first option, specify the IP address and mask of the remote network, and the interface used to access it. The following example adds a new route to eth0.

sudo ip route add 192.168.20.0/24 dev eth0

Use the ip route show command to confirm the route has been added.

ip route show

default via 178.79.148.1 dev eth0 proto static
178.79.148.0/24 dev eth0 proto kernel scope link src 178.79.148.108
192.168.20.0/24 dev eth0 scope link

For the second method, use the via keyword to specify a gateway. All traffic to the network is routed through the specified address. Replace 178.79.148.1 with your actual IP address from the output above.

sudo ip route add 192.168.20.0/24 via 178.79.148.1

To delete a route, use the ip route delete command. This command only accepts an IP address.

sudo ip route delete 192.168.20.0/24

The neigh command operates on the ARP and NDISC entries for the server’s neighbors. The neighbor command displays an address and state for each entry. An entry is REACHABLE if it is both valid and reachable, and PERMANENT if it never expires. STALE entries are valid but unreachable, and entries in the DELAY state are not yet validated. The neigh command can also edit neighbor information.

To see all the neighbors that the system is aware of, use ip neigh show.

ip neigh show

178.79.148.1 dev eth0 lladdr 00:00:0c:9f:f0:02 REACHABLE
fe80::1 dev eth0 lladdr 00:00:0c:9f:f0:02 router STALE

ARP information can be added and removed using ip neigh add and ip neigh delete commands.

Note

The delete command is useful for flushing stale ARP or NDISC information. The neigh add command can add a permanent ARP entry between two nodes that are continually communicating and have fixed IP and MAC addresses. However, a static ARP entry can cause problems if the information ever changes. Use caution when adding any entries to these tables.

To add a permanent ARP entry for a neighbor, use the following command. Include the MAC address of the neighbor and the link used to access it. The perm keyword installs the route permanently.

sudo ip neigh add 192.168.100.100 lladdr 16:12:34:56:78:90 dev eth0 nud perm
ip neigh show

178.79.148.1 dev eth0 lladdr 00:00:0c:9f:f0:02 REACHABLE
192.168.100.100 dev eth0 lladdr 16:12:34:56:78:90 PERMANENT
fe80::1 dev eth0 lladdr 00:00:0c:9f:f0:02 router STALE

Use ip neigh delete, along with the address and interface, to delete a route.

sudo ip neigh delete 192.168.100.100 dev eth0

The Linux ip command is available on all Linux distributions, including Ubuntu. It replaces the older and now deprecated ifconfig command. The ip command can display and administer the network configuration of a system. It is used to view, add, and delete network interfaces, routing table entries, and IP addresses. For more information about the ip command, see the Linux ip documentation.

More Information

You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.

• Ubuntu 22.04 Man page for the ip command
• Internet Protocol Wikipedia page
• iproute2 Wikipedia page