This is a test of NAT-traversal.

The NAT is changed such that it will not permit port 500 or 4500
to be used on origination, it blocks ESP, and it times out the connection
quickly. In addition, a second IP address is configured on NIC, and connections
on port 4500 at NAT'ed to that second IP.

2024: To have this work IKE needs to also update any IPsec state and
policy installed in the kernel.  And that has never happened.
