# Network Interface Notes

Beginning in Systemd v197, network interfaces assigned by systemd/udev are "predicatble";

Names are now based on;
* Index numbers for on-board devices (eno1)
* PCI-ehotplug slot index numbers (ens1)
* Physical/geographical location of hardware connector (enp2s0)
* MAC address (enx78e7d1ea46da)
* Classic, unpredictable kernel-native naming (eth0)

Links;
* [Predicatable Network Interface names](https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/)
* [udev-builtin-net_id.c @ freedesktop.org](https://cgit.freedesktop.org/systemd/systemd/tree/src/udev/udev-builtin-net_id.c)
* [udev-builtin-net_id.c @ github.com/systemd](https://github.com/systemd/systemd/blob/master/src/udev/udev-builtin-net_id.c#L12)

````
Two character prefixes based on the type of interface:
 *   en -- ethernet
 *   sl -- serial line IP (slip)
 *   wl -- wlan
 *   ww -- wwan
 ````
 
 [SO Answer: Find available network interfaces](https://unix.stackexchange.com/a/125401)
 
 #### Find network interface
````
ls /sys/class/net | grep -E "^e(m|n(o|p|s)|th)[0-9]|wl(an|p)"
find /sys/class/net ! -type d | xargs --max-args=1 realpath  | awk -F\/ '/pci/{print $NF}'
````

#### Find available network interfaces
````
ip r | grep " src "|cut -d " " -f 3,12 | xargs
ip addr show | awk '/inet.*brd/{print $NF}'
ip -o link show up | awk -F': ' '{print $2}'
ip -o -4 addr show
ip -o link ls up
lshw -class network
````

#### Observed Interface Names
````
em1
eno1
enp0s31f6
enp0s29u1u2
enp2s0
enp2s0f1
enp5s0
enp7s0
ens1
enx78e7d1ea46da
eth0
p7p1

wlan0
wlp0s12f0
wlp3s0
wlp3s0b1
wlp19s0

wwp0s29u1u4i6
````