US Patent 9582308 Auto detecting legitimate IP addresses using spoofguard agents

A method of blocking spoofed packets. The method receives an address allocation message from an address provisioning server that provisions addresses for virtual machines. The address allocation message includes a source address. The method stores the source address of the address allocation message. The method forwards the address allocation message to a virtual machine. The method receives, from the virtual machine, a packet with a second source address. When the second source address is the same as the first source address, the method allows the packet to be forwarded. When the second source address is not the same as the first source address, the method blocks the second packet. An additional method determines the first source address from an initial packet sent from the virtual machine instead of the address allocation method.