DNAT for routing requests to destination address

 DNAT (Destination Network Address Translation) is a networking technique that changes the destination IP address or destination port of a packet as it passes through a Linux machine.

In your case, you're using DNAT to redirect incoming traffic on port 8443 to 10.0.19.123:31108, which looks like a Kubernetes NodePort endpoint.

the command 

sudo iptables -t nat -A PREROUTING \
  -i ens5 \
  -p tcp \
  --dport 8443 \
  -j DNAT \
  --to-destination 10.0.19.123:31108