10.2 About Network Interface Names

Network interface names are based on information derived from the system BIOS or alternatively from a device's firmware, system path, or MAC address. This feature ensures that interface names persist across system reboots, hardware reconfiguration, and updates to device drivers and the kernel.

If you enable the biosdevname boot option (biosdevname=1), the biosdevname plugin to the udev device manager assigns names to network interfaces as follows:

  • Ethernet interfaces on the motherboard are named emN, where N is the number of the interface starting from 1.

  • Network interfaces on a PCI card are named pSpP, where S is the slot number and P is the port number.

  • Virtual interfaces are named pSpP_V, where S is the slot number, P is the port number, and V is the virtual interface number.

If biosdevname is set to 0 (the default), systemd naming assigns the prefixes, en, wl, and ww to Ethernet, wireless LAN, and wireless WAN interfaces respectively. The prefix is followed by a suffix based on the hardware configuration, system bus configuration, or MAC address of the device:

oN

Onboard device with index number N.

pBsS[fF][dD]

PCI device with bus number B, slot number S, function number F, and device ID D.

pBsS[fF][uP]...[cC][iI]

USB device with bus number B, slot number S, function number F, port number P, configuration number C, and interface number I.

sS[fF][dD]

Hot-plug device with slot number S, function number F, and device ID D.

xM

Device with MAC address M.

For example, an Ethernet port on the motherboard might be named eno1 or em1, depending on whether the value of biosdevname is 0 or 1.

The kernel assigns a legacy, unpredictable network interface name (ethN and wlanN) only if it cannot discover any information about the device that would allow it to disambiguate the device from other such devices. You can use the net.ifnames=0 boot parameter to reinstate the legacy naming scheme.

Caution

Using the net.ifnames or biosdevname boot parameters to change the naming scheme can rendering existing firewall rules invalid. Changing the naming scheme can also affect other software that refers to network interface names.