Some ISP's may block (seen in Bangladesh and China) ESP. Or you might suspect that the ISP limits the BW for ESP. But you dont see the same for AnyConnect clients or vpn tunnels using NAT-Traversal.
Normally NAT-T is auto negotiated, and this is in general the best way since its the default and supported
But you can force the ASA to used NAT-T for all ikev2 tunnels. The setting is not kept in nvram, so reboot clears the setting. Also you need to configured all peers with the same setting since the peers will not used NAT-T unless you force it on both sides. Or if one side is behind a NAT ip.
debug menu ikev2 4 1
