Hey there @support2bd6f6efeefcc3c0033,

Our product docs have a great section on creating custom rules in our cloud firewall.
You can use these to allow traffic through a specific port or from a specific IP.

In your situation, if you wanted to permit all traffic from a single IP, simply create the custom rule as the custom type with the port range left blank and in the source simply put the IP of the server you’d like to permit through.

https://www.digitalocean.com/docs/networking/firewalls/how-to/configure-rules/#custom-rules

Hope that helps!
- Matt.