Tuning Network Connections in Linux

I am working with a server that will act as a firewall so it will, of
course, see a lot of traffic. What is the procedure for tuning Red Hat
Linux 7.3 or 9.0 to increase the number of network connections the OS
can accept? Is there a way to see the setting? Are there any general
tuning that any of you have seen that might help?

Thanks,

Brian