In this article, you will learn how to list, configure, enable, disable, and troubleshoot network interfaces in Linux using 15 useful ifconfig commands with practical examples.
ifconfig (Interface Configuration is a utility for system/network administration in Unix/Linux operating systems used to configure, manage, and query network interface parameters via the command-line interface or in system configuration scripts.
The ifconfig command is used for displaying current network configuration information, setting up an IP address, netmask, or broadcast address to a network interface, creating an alias for a network interface, setting the hardware address, and enabling or disabling network interfaces.
ifconfig command is deprecated and has been replaced by the ip command in most modern Linux distributions. It is part of the net-tools package, which may not be installed by default on newer systems.To install it, run:
sudo apt install net-tools #Debian/Ubuntu sudo dnf install net-tools #RHEL/Fedora
1. How to List All Active Network Interfaces in Linux
The ifconfig command with no arguments will display all active network interface configuration details, including their assigned IP addresses, netmasks, and other relevant information.
ifconfig
Sample Output:
ens3 Link encap:Ethernet HWaddr 00:0B:CD:1C:18:5A
inet addr:172.16.25.126 Bcast:172.16.25.63 Mask:255.255.255.224
inet6 addr: fe80::20b:cdff:fe1c:185a/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2341604 errors:0 dropped:0 overruns:0 frame:0
TX packets:2217673 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:293460932 (279.8 MiB) TX bytes:1042006549 (993.7 MiB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:5019066 errors:0 dropped:0 overruns:0 frame:0
TX packets:5019066 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2174522634 (2.0 GiB) TX bytes:2174522634 (2.0 GiB)
tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:10.1.1.1 P-t-P:10.1.1.2 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
Note: Modern Linux distributions use predictable network interface names such as ens3, enp3s0, or eno1 instead of the traditional eth0 naming convention.
2. How to Display Information on All Network Interfaces
The following ifconfig command with the -a argument will display information on all active or inactive network interfaces on the server. It displays the results for eth0, lo, sit0, and tun0.
ifconfig -a
Sampple Output:
eth0 Link encap:Ethernet HWaddr 00:0B:CD:1C:18:5A
inet addr:172.16.25.126 Bcast:172.16.25.63 Mask:255.255.255.224
inet6 addr: fe80::20b:cdff:fe1c:185a/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2344927 errors:0 dropped:0 overruns:0 frame:0
TX packets:2220777 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:293839516 (280.2 MiB) TX bytes:1043722206 (995.3 MiB)
Interrupt:185 Memory:f7fe0000-f7ff0000
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:5022927 errors:0 dropped:0 overruns:0 frame:0
TX packets:5022927 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2175739488 (2.0 GiB) TX bytes:2175739488 (2.0 GiB)
sit0 Link encap:IPv6-in-IPv4
NOARP MTU:1480 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:10.1.1.1 P-t-P:10.1.1.2 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
3. How to View Network Settings of a Specific Interface
Using an interface name (e.g., ens3) as an argument with the ifconfig command will display configuration details for that specific network interface only.
ifconfig ens3
Sampple Output:
ens3 Link encap:Ethernet HWaddr 00:0B:CD:1C:18:5A
inet addr:172.16.25.126 Bcast:172.16.25.63 Mask:255.255.255.224
inet6 addr: fe80::20b:cdff:fe1c:185a/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2345583 errors:0 dropped:0 overruns:0 frame:0
TX packets:2221421 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:293912265 (280.2 MiB) TX bytes:1044100408 (995.7 MiB)
4. How to Enable a Network Interface
The up flag with an interface name activates a network interface if it is in an inactive state, allowing it to send and receive data.
For example, ifconfig ens3 up will activate the ens3 interface.
ifconfig ens3 up
Note: The ifup command was traditionally used as an alternative to bring interfaces up, but it is no longer available by default on many modern distributions such as RHEL 8+, Ubuntu 18.04+, and Fedora. The recommended modern approach is to use ip link set ens3 up or manage interfaces through NetworkManager using the nmcli command.
5. How to Disable a Network Interface
The down flag with an interface name deactivates the specified network interface,f or example, the ifconfig ens3 down command deactivates the ens3 interface.
ifconfig ens3 down
Note: Similar to ifup, the ifdown command is not available by default on most modern Linux distributions. Use ip link set ens3 down or nmcli as the modern alternative.
6. How to Assign an IP Address to a Network Interface
To assign an IP address to a specific interface, use the ifconfig command with the interface name and the IP address you want to set.
For example, the following command sets the IP address on the ens3 interface.
ifconfig ens3 172.16.25.125
Note: IP addresses assigned this way are not persistent and will be lost after a system reboot. To make changes permanent, configure the network through NetworkManager or by editing the appropriate network configuration files for your distribution.
7. How to Assign a Netmask to a Network Interface
Using the ifconfig command with the netmask argument and an interface name allows you to define a subnet mask for the given interface.
For example, the following command sets the netmask on the ens3 interface.
ifconfig ens3 netmask 255.255.255.224
8. How to Assign a Broadcast Address to a Network Interface
Using the broadcast argument with an interface name will set the broadcast address for the given interface. For example, the following command sets the broadcast address on the ens3 interface.
ifconfig ens3 broadcast 172.16.25.63
9. How to Assign an IP Address, Netmask, and Broadcast Address Together
To assign an IP address, netmask, and broadcast address all at once, use the ifconfig command with all three arguments as shown below.
ifconfig ens3 172.16.25.125 netmask 255.255.255.224 broadcast 172.16.25.63
10. How to Change the MTU for a Network Interface
The mtu argument sets the Maximum Transmission Unit for an interface. The MTU defines the largest size of packet (in bytes/octets) that the interface will transmit in a single transaction.
Adjusting the MTU is useful in specific network environments, such as when using VPNs or jumbo frames.
For example, the following command sets the MTU to 1000 on the ens3 interface.
ifconfig ens3 mtu 1000
Note: Not all network interfaces support MTU changes. The default MTU for Ethernet interfaces is 1500 bytes. Setting it too low can degrade performance, so change it only when required.
11. How to Enable Promiscuous Mode on a Network Interface
In normal mode, when a network card receives a packet, it checks whether the packet is addressed to itself. If not, it drops the packet. In promiscuous mode, the network interface accepts all packets flowing through the network, regardless of their destination address.
Network monitoring and packet analysis tools such as tcpdump and Wireshark rely on promiscuous mode to capture traffic.
To enable promiscuous mode on an interface, use the following command.
ifconfig ens3 promisc
12. How to Disable Promiscuous Mode on a Network Interface
To disable promiscuous mode and return the network interface to normal operation, use the -promisc switch as shown below.
ifconfig ens3 -promisc
13. How to Add an Alias to a Network Interface
The ifconfig utility allows you to configure additional IP addresses on the same physical interface using the alias feature, which is useful when you need a single interface to respond to multiple IP addresses.
To add an alias for the ens3 interface, use the following command, but do note that the alias IP address must be within the same subnet as the primary IP address.
For example, if your primary IP is 172.16.25.125, a valid alias would be 172.16.25.127.
ifconfig ens3:0 172.16.25.127
Next, verify the newly created alias interface by running the following command.
ifconfig ens3:0
Sample Output:
ens3:0 Link encap:Ethernet HWaddr 00:01:6C:99:14:68
inet addr:172.16.25.127 Bcast:172.16.25.63 Mask:255.255.255.224
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Note: Interface aliases are not persistent across reboots. For permanent multiple IP addresses on a single interface, configure them through NetworkManager or the distribution-specific network configuration files.
14. How to Remove an Alias from a Network Interface
If you no longer require an alias network interface or configured it incorrectly, you can remove it using the following command.
ifconfig ens3:0 down
15. How to Change the MAC Address of a Network Interface
To change the MAC (Media Access Control) address of a network interface, use the ifconfig command with the hw ether argument followed by the new MAC address. Note that the interface must be brought down before changing its MAC address on some systems.
ifconfig ens3 down ifconfig ens3 hw ether AA:BB:CC:DD:EE:FF ifconfig ens3 up
Note: MAC address changes made this way are temporary and will revert after a reboot. For permanent changes, use ip link or configure it through NetworkManager.
These are the most useful ifconfig commands for configuring network interfaces in Linux. For more information and usage options, refer to the man page by running man ifconfig at the terminal.
Since ifconfig is deprecated on most modern Linux distributions, it is worth familiarizing yourself with the ip command as the recommended replacement for managing network interfaces going forward.
Other Networking Utilities
- nmcli – a command-line client that is used to control NetworkManager and report network information.
- Tcmpdump – is a command-line packet capture and analyzer tool for monitoring network traffic.
- Netstat – is an open-source command-line network monitoring tool that monitors incoming and outgoing network packet traffic.
- ss (socket statistics) – a tool that prints network socket-related information on a Linux system.
- Wireshark – is an open-source network protocol analyzer that is used to troubleshoot network-related issues.
- Munin – is a web-based network and system monitoring application that is used to display results in graphs using rrdtool.
- Cacti – is a complete web-based monitoring and graphing application for network monitoring.
To get more information and options for any of the above tools, see the man pages by entering “man toolname” at the command prompt. For example, to get the information for the “netstat” tool, use the command “man netstat“.
