NAT-T is used to detect NAT device in the path and change port to UDP 4500. This UDP port 4500 is used to PAT ESP packet over ipsec unaware NAT device. if this UDP encapsulation in not done then the ESP packet will be dropped and data will not flow. well my question is : the ESP packet starts after 9 th packet of quick mode. but the NAT-T is detected and changes the port from udp 500 to 4500 on 5th packet. why is this done on 5th packet, is there any particular reason to do this in 5th packet.
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