I installed proxmox 4.4 on virtualbox and after installation I am not allowed to access to internet.
when i ping 8.8.8.8 I got a "network unreacheble"
My host and the vm are in the same IP rank. I can access to proxmox interface via my browser
I suggest you check your VMs networking config (in vbox). It sounds a lot like you have "host only" networking configured. "Bridged" is what you'll want.