IPSec VPN is a layer 3 protocol that communicates over IP protocol 50, Encapsulating Security Payload (ESP). It might also require UDP port 500 for Internet ...
Ports Used for IPSec ; 4500. UDP. Port used by IKE on the management plane to connect with remote IKE peers. ; 4510. UDP. Port used by the dataplane to send ...
Ipsec needs UDP port 500 + ip protocol 50 and 51 - but you can use NAt-T instead, which needs UDP port 4500. On the other hand L2TP uses udp port 1701.