Monitoring bandwidth usage of all virtual machines

[cyberygan]

We have VMware Server installed on CentOS, and there are 8 virtual machines running on it. I am wondering if there is anyway to monitor all network traffic of each virtual machine. Although we can enable SNMP on each VM, but is there an easier way to do this?
I searched, and only found ESX related solution, but we are using the free VMware Server.
Thanks.