Network interface name

The Linux kernel assigns names to network interfaces, nowaday there are multiple network interface naming scheme is available and each has pros and cons.

Simple scheme

eth0, eth1, etc were simply assigned by the kernel.

There are many possible way to use this scheme,

• . reboot with the kernel parameter net.ifnames=0, or made persistent by editing /etc/default/grub and running update-grub

• override /lib/systemd/network/99-default.link, with a custom version in /etc/systemd/network/, or similarly override /lib/udev/rules.d/80-net-setup-link.rules, or mask the latter by using a /dev/null symlink instead of a custom version, or...

Persistent names scheme

udev to identify interfaces by MAC address and assign a fixed interface number to any interface by writing the rules to /etc/udev/rules.d/xxx.rules

for example,

#/etc/udev/rules.d/70-persistent-net.rules
# PCI device 0x8086:0x100e (e1000e)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="aa:bb:cc:dd:ee:ff", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"

Predictable names scheme

Predictable Network Interface naming and is part of systemd, to which Ubuntu has been transitioning as of version 15.04. the idea is to set interface name depends on physical location of hardware and can be predicted/guessed by looking at lspci or lshw output.

There are 3 ways how interface name is assigned, Refer here for more

1. based on BIOS/Firmware for onboard cards
2. based on PCI information
3. based on MAC address of the interface

Custome names scheme

Using systemd.link

#/etc/systemd/network/10-persistent-net.link
[Match]
MACAddress=01:23:45:67:89:ab

[Link]
Name=lan0

To verify the new policies to work after a reboot,

• run udev control --reload (or /etc/init.d/udev force-reload, or service udev force-reload)
• then
  • for hotplug NICs, disconnect and reconnect them (or unload/reload the driver; if your SSH session doesn't go through this NIC...)
  • for non-hotplug NICs, run udevadm trigger, then check the logs (your SSH connection should still be okay even if your .link file was rejected as nonsense), then restart networking.

It is also possible to reorganize the naming policy by overriding /lib/systemd/network/99-default.link, for instance to insist that all network interfaces are named purely by MAC address:

 #/etc/systemd/network/99-default.link
 [Match]
 OriginalName=*

 [Link]
 NamePolicy=mac
 MACAddressPolicy=persistent