block 1 IP outbound to only 1 Internet ip address

Hey guys, i have a ip within my network 172.16.0.24 that i want to block all access to the internet except for lets say 123.123.123.123 on the internet. I want it so it can only talk to that ip on the internet, this ip would be my VPN server, if my device 172.16.0.24 lost connection to the VPN server it would not have any internet access out my regular ISP. i assume i have to do this in the CLI with iptables just trying to figureout the right commands to use.

Thanks