The default nat-policy is always mandatory and must be configured under the router/vprn>nat>inside context. This default NAT policy can reference any configured pool in the needed ISA group. The pool referenced in the default NAT policy can be then overridden by the NAT policy associated with the destination-prefix in LSN44 or by the NAT policy referenced in the ipv4/ipv6-filter used for NAT diversion in LSN44/DS-Lite/NAT64.
The NAT CLI nodes fail to activate (be brought out of the no shutdown state), unless a valid NAT policy is referenced in the router/vprn>nat>inside context.