In case anyone else might find this useful, I created operational commands to show a 5 second sample of ethernet/vif traffic.
Should be extendable to any interface that shows up in /proc/net/dev.
Install:
wget -q -O - https://dl.dropboxusercontent.com/u/19515814/vyos-traffic-install.sh | /bin/sh
Output:
user@vyos:~$ show interfaces ethernet eth0 traffic
RX Mbps : 274.2
RX PPS : 36966
RX BPP : 972
RX errors: 0
RX drops : 0
TX Mbps : 87.0
TX PPS : 30996
TX BPP : 368
TX errors: 0
TX drops : 0
user@vyos:~$ show interfaces ethernet eth0 vif 80 traffic
RX Mbps : 267.2
RX PPS : 29045
RX BPP : 1205
RX errors: 0
RX drops : 0
TX Mbps : 68.2
TX PPS : 27466
TX BPP : 325
TX errors: 0
TX drops : 0