How do blockchains fight symmetrical NAT?

Question

Computer networks

Networks like bitcoin or ethereum, as you know, do not use known NAT piercing mechanisms, everywhere they write like this is not necessary. It seems like the only thing they use is UPnP. The thing is good, but I tested it on symmetrical NAT, and it is useless there. It will not be possible to open a connection with such a NAT until he wants to initiate it himself.

Answer 1

No way :)
Blockchain is a linked list containing information. When transferring it, he will use the mechanisms that are provided by the creators of the program that uses the blockchain :) And it will be ISO7.
NAT is on ISO3 and when changing the address, it has no idea what the package has in the "cargo" part - blockchain or boobs ...

Answer 2

If you use UDP, then you can use TURN and other things that are used in Voip where this problem is very relevant.
https://en.wikipedia.org/wiki/Traversal_Using_Rela...
https://en.wikipedia.org/wiki/STUN
https://en.wikipedia.org/wiki/Interactive_Connecti...

Answer 3

On the Internet there will always be computers with an external ip