NetworkManager & Symlink interface names

Question

I have a Nimbelink modem that enumerates as 4 ttyUSB devices. I'd like to have persistent interface names so NetworkManager can control the ppp0 connection (need to use the 3rd ttyUSB of the 4).

I've set up rules in /etc/udev/rules.d to create symlinks. All of that seems to work fine. I can communicate AT commands using picocom with the symlink. Doing:

udevadm info --query=path --name=/dev/ttyUSB_modem2

shows that it correctly links to the third ttyUSB interface from the modem regardless of where it falls in /dev.

I think my issue is NetworkManager isn't using/recognizing the symlink as the interface name after I set it using the nmcli connection editor. If I change the name back to ttyUSB2 (assuming the modem enumerates as ttyUSB[0-4]), it connects fine. Is this possible with NetworkManager? Ultimately, I'd like the modem to act as a backup for a wired Ethernet connection.

OS: Headless version of Debian 9

Answer 1

First stack exchange question ever, and I'm answering it myself (jeez). The NetworkManager doesn't need an interface name, apparently:

nmcli connection edit ppp0
nmcli>set connection.interface-name *type nothing*
Enter 'interface-name' value: *hit enter*
save
quit

Don't enter the interface name and the NM discovers it.

configure gsm connection using nmcli