&gt; A 6in4 address ends in an IPv4 address so it doesn&#x27;t actually add any IP space: A 6in4 host can&#x27;t allocate additional IPv6 addresses that are routed over IPv4.<p>Not so - if you have a single public IPv4 address you can turn that into an IPv6 &#x2F;48 and put up to 16 bits worth of hosts behind it. Given that these are only for edges and not meant to have routing within them that should be plenty (having two different sets of routing logic applying to the same packets would be a recipe for difficult-to-debug disconnections and even-more-difficult-to-debug transient slowness).