Trying to limit a staging server to a specific set of IP's that can access it. How would I do this for iptables or is there a better way to do it?
If you're going to have more than one or two servers, I'd make a new chain for your service. Set up a rule on the INPUT chain to jump to that new chain, set the default policy on the new chain to REJECT, and then just insert rules to ACCEPT when the source is any of the allowed machines.
You just run that last line over and over with additional IPs.