How to request addresses for each instance in a service

Archive Rancher 1.x
1

I’d like to pre-allocate IP addresses for each instance in a service, I’ve tried this with 3 container instances:

::
launchConfig = {
…
“requestedIpAddress”: [“IP1”, “IP2”, “IP3”]
…
}

but it turns out only IP1 was signed to the first container instance.
My question is: Is it possible to do this? and How to do it if it is?