gatling is using all ephemeral port range available

Gatling (Open-Source)
1

i am running below scenario. could able to see gatling using all ephemeral port range available leading failure.
as per documentation i could see by default keep-alive is true. i have specified 5000 users and expect 5000 connections should be establised and maintain 50Rps and 100 Rps.

writers.inject(nothingFor(10 seconds),rampUsers(5000) over(10 seconds))
.throttle(
reachRps(50) in (1 seconds),
holdFor(3 hours),
jumpToRps(100),
holdFor(3 hours)

do i need to change any gatling.conf to limit the connections?