, section 4, "Changing to New Ports",

"Any implementation that supports NAT traversal MUST support
negotiations that begin on port 4500. If a negotiation starts
on port 4500, then it doesn't need to change anywhere else
in the exchange."

So, I've been digging through the documentation looking for how to
convince a RAS entry to do this ... and haven't figured it out yet.

Anybody else done this yet?