René,
Congrats for share this excellent explanation!!! I’m from Brazil and I don’t have a good English, but I can understand each word, sentence that you used in this article. I never had understood about this subject, maybe because I really didn’t study it with attention and deeply. I’m a beginner Network Admin and when I saw this article in my feed I started to read it and understand it and I’m amazing how you can teach it like this way.
But I have a doubt where I can’t see in examples above. Using this topology, if tomorrow for any reason Blue and Red make a partnership and decide them share your resource between hosted at Blue1 and Red2. How could ISP route the traffic between them?Maybe this article contain the answer, but I can see it.
Again, Thanks for share your knowledge, keep it and go ahead!!!
P.S: Sorry for my English mistakes, but I’m not a native English speaker.
Hugs