[Busla]

ВОт нашел по L2TP: UDP: порт 1701, UDP порт 500 , UDP порт 4500. »

нет:

Код:

The initiator of an L2TP tunnel picks an available source
UDP port (which may or may not be 1701), and sends to the desired
destination address at port 1701.  The recipient picks a free port on
its own system (which may or may not be 1701), and sends its reply to
the initiator's UDP port and address, setting its own source port to
the free port it found.

500 и 4500 - это не про l2tp, а про ipsec