Create

$ vultr-cli vpc nat-gateway port-forwarding-rule create <VPC ID> <NAT Gateway ID> [flags]

# Full example
$ vultr-cli vpc nat-gateway port-forwarding-rule create e3512e83-64e9-4d3e-a401-9b86f2e09b1d \
efc811e7-d07d-45b1-b50e-19a0c2936ce0 --name="example-rule" --description="example desc" --internal-ip="10.1.2.3" \
--protocol="tcp" --external-port="123" --internal-port="555" --enabled="true"

--description is optional. Everything else is required

# Shortened example with aliases
$ vultr-cli vpc ng pfr c e3512e83-64e9-4d3e-a401-9b86f2e09b1d efc811e7-d07d-45b1-b50e-19a0c2936ce0 -n="example-rule" \
-d="example desc" --internal-ip="10.1.2.3" -p="tcp" --external-port="123" --internal-port="555" -e="true"