Virtual server connection limite through iRule

You can probably reference this other DevCentral post to get most of the way to your goal, https://devcentral.f5.com/s/question/0D51T00006i7TIA/connection-limit-on-virtual-server

The iRule below is an example I created but has not been tested for functionality or requirements.

when RULE_INIT {
	set ::active_connections 0
	set ::max_connections 3000
}
when CLIENT_ACCEPTED {
	#Check if we're over the maximum allowed connections
	if {$::active_connections > $::max_connections } {
		# We're over the max, send to pool B
		pool B
	} else {
		# We're not over the max, so send to Pool A and increment active_connections
		incr ::active_connections 1
		pool A
	}
}
when CLIENT_CLOSED {
	# A connection was closed, so decrement the global counter
	incr ::active_connections -1
}