RT-AC66U B1 (386.3_2) - how to measure just WAN traffic?

[tmcatalin]

Hi,
I found that in RT-AC66U B1 (and not only) eth0 is including the LAN traffic. Is it a way to measure just WAN traffic?
I am using Vnstat with measurement of eth0 but having a lot of traffic with the my NAS the eth0 statistics are relevant for my use case.
Are the creation of VLAN and interface the only solutions? If yes, can you direct me to a tutorial?
Thanks

PS: below picture is from RT-AC68U and I supposed similar config is on AC66U:

 

[ColinTaylor]

Check your numbers again as this should not be possible. Check you are monitoring the correct interface. The WAN interface will either be vlan2 or eth0 depending on whether or not hardware acceleration is enabled. But if hardware acceleration is enabled the numbers reported will be incorrect.