VZSpeed
OpenVZ container network usage measuring tool
Setup
Either clone or wget the vzspeed file into /bin/ so that you can access it directly as a command. An alternative is to wget/clone it elsewhere and then add a entry into your .bashrc file. You'll need to chmod file as well, chmod +x should be enough.
Usage
vzspeed <VMID>
For example,
[root@test ~]# vzspeed 100
100| TX: 32087 kB/s RX: 3 kB/s
100| TX: 8171 kB/s RX: 0 kB/s
100| TX: 15508 kB/s RX: 2 kB/s