I’ve made some progress with this but I’m puzzled over the interfaces I want to monitor. I’m thinking I really only want stats from my WAN connection, whether that is tethered over a 3G/4G phone or wired to the WAN port or with a WISP connection to my home wifi. At the moment I’m only using the WISP function.

In LuCI, Vnstat is giving me these choices:

apcli0 (wwan, ethernet)
br-lan (lan)
eth0 (switch)
eth0.1 (lan)
eth0.2 (wan, wan6)
ra0 (ethernet)

From the parentheticals I thought I should be looking at apcli0 and / or eth0.2, but after several days there is zero traffic on apcli0, and only transmitted traffic on eth0.2. I’m guessing apcli0 may be solely for USB tethering, so that is okay, but I thought I should see much more received traffic.

On ra0 I have a lot of received/transmitted traffic.

Thoughts?