Hello, Marius!
Thank you very much for your explanation. If I understand you correctly, this is not quite the usual mechanism is made to minimize the inconvenience of the used tunneling technology.
Apparently, we are talking about the tunnels in the style of RFC-1853, a.k.a. NOS IPIP. Are they still used in common practice? Now is not 1993. The times of the legendary ka9q.exe long gone and there are many good solutions. That works through the NAT, allows clients to use a dynamic address and have reliable authorization.
Why still KA9Q/NOS? This is good old British tradition?
And I have a different question - why each network node must constantly keep and update a full map of the routes during the entire network? Unforgettable encap.txt from my youth... What topological model is implemented in a network now?
I'm sorry for a lot of questions, but I was expecting something other.