You can use the iptables command to limit the number of connections per IP address on a Linux system. To do this, you can use the connlimit module in conjunction with the --connlimit-above option.
Here's an example of how to use the connlimit module to limit the number of connections per IP to 10:
iptables -A INPUT -p tcp -m connlimit --connlimit-above 10 -j REJECT
This will reject any incoming TCP connections that exceed a rate of 10 connections per IP address.
You can also specify the protocol and port number using the -p and --dport options, respectively:
iptables -A INPUT -p tcp --dport 80 -m connlimit --connlimit-above 10 -j REJECT
This will reject any incoming TCP connections on port 80 that exceed a rate of 10 connections per IP address.
Note that the connlimit module is not available in all versions of iptables. If it is not available on your system, you may need to install it or use a different method to limit connections per IP.