The network interfaces assumed in the script are eth0 and eth1.
However, sometimes in case of a VM, the interfaces might get changed to something like eth2 and eth3. In such a case, the script needs to be grepped and replaced properly.
A more suitable approach would be to have eth0 and eth1 as default interfaces and have a way to pass the desired interfaces from the command line.
Eg., python cloudgear.py -m -i