ip: command not found

You can use the ip command to display the status of an interface, configure network properties, or for debugging or tuning the network. The ip command replaces the ifconfig command, which is deprecated. The syntax of the ip utility follows:

# ip [OPTIONS] OBJECT {COMMAND | help}

ip command provides a number of OBJECT arguments, such as:
– link: Network device
– address (or addr): IPv4 or IPv6 address on a device
– route: Routing table entry

It also provides a number of COMMANDS for each OBJECT, such as:
– add, change, del, show, more

If you encounter the below error while running the command ip:

ip: command not found

you may try installing the below package as per your choice of distribution:

Below are few of the most commonly used ip command examples in Linux.

The ip addr sub-command

1. Show current network configuration

Use the ip addr object to show and manage IPv4 or IPv6 address on a device. The following example shows IP status for all active devices. The show command is the default.

# ip addr show

2. Assign IPv4 Address to a network interface

The following example uses the add argument to add the IPv4 address 172.31.29.90/20 to the eth0 interface. The show argument is given afterwards to display the result. The show argument is given afterwards to display the result. This example assumes the interface already has 172.31.124.62/20 assigned to it.

# ip addr add 172.31.29.90/20 dev eth0

# ip addr show eth0
2: eth0: [BROADCAST,MULTICAST,UP,LOWER_UP] mtu 9001 qdisc pfifo_fast state UP qlen 1000
    link/ether 06:e6:41:84:10:48 brd ff:ff:ff:ff:ff:ff
    inet 172.31.124.62/20 brd 172.31.127.255 scope global dynamic eth0
       valid_lft 3311sec preferred_lft 3311sec
    inet 172.31.29.90/20 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::4e6:41ff:fe84:1048/64 scope link 
       valid_lft forever preferred_lft forever

3. Delete IPv4 Address from an interface

Use the del argument to delete the IPv4 address. Example:

# ip addr del 172.31.29.90/20 dev eth0

# ip addr show eth0
2: eth0: [BROADCAST,MULTICAST,UP,LOWER_UP] mtu 9001 qdisc pfifo_fast state UP qlen 1000
    link/ether 06:e6:41:84:10:48 brd ff:ff:ff:ff:ff:ff
    inet 172.31.124.62/20 brd 172.31.127.255 scope global dynamic eth0
       valid_lft 3248sec preferred_lft 3248sec
    inet6 fe80::4e6:41ff:fe84:1048/64 scope link 
       valid_lft forever preferred_lft forever

4. Flush all IPv4 Addresses assigned to an Interface

Use the flush argument to remove all the IPv4 addresses assigned to an interface. Example:

# ip addr flush dev eth0

The ip link Sub-command

Use the ip link object to show and manage the state of network interface devices on the system. Below are some of the common usage of the ip link sub-command.

1. Check the status of network devices

The following example shows the status of all active devices. The show argument is the default. Notice that the output is similar to that of the ip addr command, but without the IP address information.

# ip link show

2. Up/Down the network interface

Use the set argument to change device attributes. The up and down arguments change the state of the device. The following example brings the eth0 interface down and then back up. The show argument displays the results of the set argument.

# ip link set eth0 down

# ip link show eth0
2: eth0: [BROADCAST,MULTICAST] mtu 9001 qdisc pfifo_fast state DOWN mode DEFAULT qlen 1000

# ip link set eth0 up

# ip link show eth0
2: eth0: [BROADCAST,MULTICAST,UP,LOWER_UP] mtu 9001 qdisc pfifo_fast state UP mode DEFAULT qlen 1000
    link/ether 06:e6:41:84:10:48 brd ff:ff:ff:ff:ff:ff

3. Change the MTU attribute

The following example uses the set argument to change the MTU attribute to 1000:

# ip link set eth0 mtu 1000

# ip link show eth0
2: eth0: [BROADCAST,MULTICAST,UP,LOWER_UP] mtu 1000 qdisc pfifo_fast state UP mode DEFAULT qlen 1000
    link/ether 06:e6:41:84:10:48 brd ff:ff:ff:ff:ff:ff

ip neigh sub-command to administer ARP table

ARP resolves an IP address to the MAC address. The MAC address is a 48-bit physical hardware address, which is burned into the network interface card (NIC). Network applications use the IP address to communicate with another device but the MAC address is needed to ensure network packets are delivered.

Use the ‘ip neigh‘ sub-command to display the ARP table, to delete an ARP entry, or to add an entry to the table. The ip neigh sub-command replaces the arp command, which is deprecated. The ARP table is also known by another name, the IP neighbor table.

The ip neigh object commands are summarized as follows:

1. Display ARP table

The following example displays the ARP table. The show command is the default.

# ip neigh
172.31.112.1 dev eth0 lladdr 06:75:25:15:b5:ba REACHABLE

2. Clear all the ARP table entries

The following example clears all entries in the ARP table with verbosity:

# ip -s -s neigh flush all
172.31.112.1 dev eth0 lladdr 06:75:25:15:b5:ba ref 1 used 33/0/29 probes 1 REACHABLE
*** Round 1, deleting 1 entries ***
*** Flush is complete after 1 round ***

3. Remove ARP table entries for a specific interface only

The following example removes entries in the ARP table on device eth0:

# ip neigh flush dev eth0

ip route sub-command

The ip route utility displays or manipulates the IP routing table. Its primary use is to set up static routes to specific hosts or networks through a network interface.

1. Displaying the Routing Table

Use the ip route command to display the routing table. Example:

# ip route
default via 172.31.112.1 dev eth0 proto static metric 100 
172.31.112.0/20 dev eth0 proto kernel scope link src 172.31.124.62 metric 100

You can also use the old good ‘netstat -r’ command to display the routing table.

# netstat -r
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
default         gateway         0.0.0.0         UG        0 0          0 eth0
172.31.112.0    0.0.0.0         255.255.240.0   U         0 0          0 eth0

2. Adding a Route

Use the ip route add command to add a static route. The following example adds a default route, which is used if no other route matches. All network packages using this route are “gatewayed” through the 172.31.112.1 IP address:

# ip route add default via 172.31.112.1 dev eth0 proto static

The following example adds a static route to a host address via a specific network interface.

# ip route add 192.0.2.1 via 10.150.36.2 dev eth0

3. Delete a route

Use the ip route delete command to delete an entry from the routing table, for example:

# ip route delete default via 172.31.112.1
# ip route delete 192.0.2.1

4. Configuring Permanent Static Routes

Any changes that you make to the routing table by using ip route do not persist across system reboots. To make static routes permanent, configure them for each interface. Static route configuration is stored in a /etc/sysconfig/network-scripts/route-interface file. For example, static routes for the eth0 interface would be stored in the /etc/sysconfig/network-scripts/route-eth0 file.
The route-interface file has two formats:

• IP command arguments
• Network/netmask directives

The IP command arguments format uses the following syntax:

x.x.x.x/x via x.x.x.x dev interface

Use the term default to create a default gateway, for example:

default via x.x.x.x dev interface

The following example creates a static route to the 192.168.2.0/24 subnet through an eth0 interface (10.10.10.1):

# cat /etc/sysconfig/network-scripts/route-eth0 198.168.2.0/24 via 10.10.10.1 dev eth0

You can also use the network/netmask directives format for route-interface files. The format is as follows:

ADDRESS0=X.X.X.X NETMASK0=X.X.X.X GATEWAY0=X.X.X.X

The following example shows use of the IP command arguments to define the same entry:

ADDRESS0=198.168.2.0
NETMASK0=255.255.255.0
GATEWAY0=10.10.10.1

Start at 0 (as shown) and increment by one for each additional static route.