Detach the network card, keep every identity attached to it.
An ENI's IPs, Elastic IP, and MAC address all move with it to a new instance.
Elastic IP
Static public IPv4, yours until released — unlike an auto-assigned IP that changes on every stop/start
ENI
Private IP + EIP + MAC + Security Groups, detachable from one instance and attachable to another
The ENI hot-swap is still the real fix for stateful workloads an Auto Scaling Group can't simply replace — a licensed appliance, anything where the network identity itself must survive the failure.