How to use ip command to manage network in Linux

The most basic part of Linux administration and troubleshooting is checking the IP configuration of a system to ensure that the system has a valid IP and is accessible on the local network.

The ip command in Linux is a powerful tool that not only displays the current IP address of your system, but also allows you to view and manage the current configuration of network interfaces, IP addresses, routing, and ARP tables.

Let's look at some common use cases of the ip command in Linux.

Finding IP Address on Linux

To find the IP address of a Linux system, use the ip command followed by address, addr, or options:

 linuxmi@linuxmi/home/linuxmi/www.linuxmi.com​​​​​​​​​​
⚡ ip address

This will display the configuration of all network interfaces, including their IP addresses.

In the following example, you can see that the system has three network interfaces: lo (loopback address), ens33. The output includes the following information:

• Layer 1 information, such as interface capabilities and physical layer connection status, MTU, operational state of the interface (for example, UP or DOWN), and transmit queue length (qlen).
• Layer 2 information, such as the MAC address of the interface.
• Layer 3 information includes the IP address and its type (dynamic IP addressing or static IP addressing).

To display brief information about a network interface, use the ip command with the –brief option as follows:

 linuxmi@linuxmi/home/linuxmi/www.linuxmi.com​​​​​​​​​​
⚡ ip -- brief address show

To display only IPv4 address information, use the following command:

 linuxmi@linuxmi/home/linuxmi/www.linuxmi.com​​​​​​​​​​
⚡ ip - 4 addr

To find the IP address information for a specific network interface, use the following syntax:

 ip address show dev [ interface ]

For example, to view the IP address of network interface ens33, the command is:

 linuxmi@linuxmi/home/linuxmi/www.linuxmi.com​​​​​​​​​​
⚡ ip address show dev ens33

Viewing and Changing the MAC Address

Using the ip command, you can also view and change the MAC address of your system.

To view the MAC address of your Linux system, use the following command:

 linuxmi@linuxmi/home/linuxmi/www.linuxmi.com​​​​​​​​​​
⚡ ip -- brief link show

To view the MAC address of a specific interface, use:

 ip -- brief link show dev [ interface ]

To change the MAC address, first shut down the interface:

 sudo ip link set dev [ interface ] down

Then change the MAC address of the interface using the following command:

 sudo ip link set dev [ interface ] address [ new - mac - adddress ]

After that, call up the interface:

 sudo ip link set dev ens33 up 

View network interface statistics

You can also use the ip command to view the statistics of the network interface. Use the following ip command to view the statistics of all network interfaces on the system:

 linuxmi@linuxmi/home/linuxmi/www.linuxmi.com​​​​​​​​​​
⚡ ip - s link

The output includes statistics such as transmitted and received bytes/packets, errors, dropped packets, multicast, etc. To display statistics for a specific interface, use the following syntax:

 linuxmi@linuxmi/home/linuxmi/www.linuxmi.com​​​​​​​​​​
⚡ ip - s link show dev ens33

Use ip to modify link properties

To bring up the interface, use the following ip command:

 sudo ip link set [ interface ] up

To shut down the interface, run:

 sudo ip link set [ interface ] down

You can also change the MTU (Maximum Transmission Unit) of an interface using the following command:

 sudo ip link set mtu [ number ] dev [ interface ]

For example, to set the MTU of network interface ens33 to 8000, the command is:

 linuxmi@linuxmi/home/linuxmi/www.linuxmi.com​​​​​​​​​​
⚡ sudo ip link set mtu 8000 dev ens33

Adding/Removing IP Addresses on Linux

To add an IP address to a network interface, use the following syntax:

 ip addr add [ ip - address ] dev [ interface ]

To add the IP address 192.168.42.140/24 to the network interface ens33, the command is:

 linuxmi@linuxmi/home/linuxmi/www.linuxmi.com​​​​​​​​​​
⚡ sudo ip addr add 192.168 .152 .130 / 24 dev ens33

Use this command syntax to remove an IP address from an interface:

 ip addr del [ ip - address ] dev [ interface ]

For example, to delete the IP address 192.168.152.130/24 from the interface ens33, the command is:

 linuxmi@linuxmi/home/linuxmi/www.linuxmi.com​​​​​​​​​​
⚡ sudo ip addr del 192.168 .152 .130 / 24 dev ens33

Viewing the Routing Table on Linux

The ip route command is used to view and modify routes in a Linux system. To display the system's routing table, use the ip route command without any options:

 linuxmi@linuxmi/home/linuxmi/www.linuxmi.com​​​​​​​​​​
⚡ ip route

Each line in the output represents a configured route. A route consists of the destination network address, the next hop (i.e. the IP address of the router), the interface to send the packet to, and the metric (a value used to determine the preferred route when there are multiple routes to reach the destination). In this case, the route with the lower metric is preferred.

In the example above, the first two entries represent the default route, which is used when no other route is available for the destination address. 192.168.174.2 is the IP address of the router. dev ens33 indicates the interface that will be used to send packets to the router. The proto dhcp field indicates that the default route was learned from DHCP.

The second entry represents the APIPA address (Automatic Private IP Addressing) 169.254.0.0/16. When a host fails to obtain an IP address from the DHCP server, it assigns itself a random IP address from this network. It allows them to communicate with other hosts in the subnet that also failed to obtain an IP address.

The src field indicates the IP address of the interface used as the source address when sending packets through this route.

Use ip to modify the routing table

To add a route manually, use the ip route command followed by the destination network address and the gateway IP:

 sudo ip route add [ network - id ] via [ gateway - ip ]

For example, to add a route that sends all traffic destined for the 192.168.30.0 network to the gateway at 192.168.174.2, you would use the following command:

 sudo ip route add 192.168 .30 .0 / 24 via 192.168 .174 .2

Add a default route using the following command:

 sudo ip route add default via [ ip - address ] dev [ interface ]

For example, to add a default route that directs traffic to router 192.168.30.1 through ens33, the command would be:

 sudo ip route add default via 192.168 .30 .1 dev ens33
 ip route get [ ip - address ]

To delete a routing table entry, use the following syntax:

 sudo ip route delete [ network - address ] via [ gateway - ip ]

You can also see the route an address will take using the following syntax:

 ip route get [ ip - address ]

Managing neighbor tables on Linux

In Linux, you can use the ip neigh command to view and modify the neighbor table, also known as the ARP table. To view the current neighbor table entries, use the following command:

 linuxmi@linuxmi/home/linuxmi/www.linuxmi.com​​​​​​​​​​
⚡ ip neigh show

To add a new entry to the neighbor table, use the following syntax:

 sudo ip neigh add [ ip - address ] lladdr [ mac - address ] dev [ interface ]

To delete an entry from the neighbor table, use the following syntax:

 sudo ip neigh del [ ip - address ] dev [ interface ]

Add colors to the output of the ip command

To make the output easier and faster to understand, you can add colors to the ip command output using the -c option:

 linuxmi@linuxmi/home/linuxmi/www.linuxmi.com​​​​​​​​​​
⚡ ip - c a

Managing Networks and IP Addresses on Linux

The ip command in Linux is a useful tool for managing and troubleshooting network connections. From viewing network interfaces and modifying link properties to finding IP addresses and managing routes, the ip command allows you to perform many system administration tasks from the command line.