Per ip connection limit on virtual server

Thankyou both for your replies - and my mistake for NOT clarifying my requirements .

here is my scenario 

i have a application virtual server 

i want to apply per ip connection limit on it . meaning ip address 20.20.20.20 - can have a max of 50 connection , and should never exceed that number.

as i understand - connection limit is total connection on a virtual server - so it is NOT pet source ip .

and rate limit is counted per second - meaning is i apply rate limit of 30 per second - it NOT allow more than 30 sessions in a second but it does not stop sessions slowly increasing to 500.

Hope this clarifies

Thanks