1. A system comprising: a first server device executing a first virtual machine and connected to a physical network; a second server device executing a second virtual machine and connected to the physical network, wherein the first and second virtual machines are connected to a same virtual network; a first firewall module that functions as a firewall for the first virtual machine and a second firewall module that functions as a firewall for the second virtual machine, the firewall modules configured to filter network traffic received by the physical servers and addressed to the respective virtual servers; wherein the first firewall module is executed by a core processor of the first virtual machine and the second firewall module is executed by a core processor of the second virtual machine; wherein the first and second firewall modules each include a superset of the same firewall rules.