Forwarding Protocol 41 in NAT Boxes
Some NAT boxes/routers allow the establishment of IPv6 tunnels from systems in the private LAN (using private IPv4 addresses) to routers or tunnel servers in the public Internet. As far as we know this is not a common way of use IPv6 tunnels; the usual way is to finish the tunnel directly in a device with an IPv4 public address. This behavior provides a big opportunity to rapidly deploy a huge number of IPv6 nodes and networks, without the need of new transition mechanism. This option is very important to facilitate the IPv6 deployment. This document describes this behavior and provides hints that should be applied in the NAT boxes and tunnel brokers to facilitate it.