Hi, I wish to create an IP in IP tunnel interface that works as follows: At the sender: * The interface checks the dst IP address on the IP packet that it receives. * It encapsulates the IP packet inside another IP packet with: Field 1: source address = the interface's IP address Field 2: dst address = the packet's dst IP address * The interface now transmits the packet This is different from normal IPinIP tunnels because it is not point-to-point. The operation in Field 2 is similar to NAT. Also, this is different from SNAT, because I want the receiver to know what the original source IP. At the receiver, assume that there is a stack that understands this special IPinIP packet and has a way to handle it. If it's too specific, then I do not mind implementing it. Thanks, -- Vimal