Foreman DHCP on two subnets

my Foreman machine acts as DHCP server / smart proxy for the subnets it
It has two different virtual NICs, serving two different subnets, but the
subnets can actually communicate between them through the corporate LAN.

What happens when I create a new virtual machine via Foreman (on a VMware
compute resource) is that Foreman correctly adds the static DHCP lease for
the subnet I choose during VM setup, but when the VM boots up its
DHCPDISCOVER reaches both NICs on the Foreman machine, and sometimes it
happens that Foreman also creates anyway a dynamic lease inside the other
subnet for the same machine.
This creates a problem in that the new machine sometimes gets an IP for a
subnet, sometimes it gets one for the other.

Is there a way to prevent this? I thought the static lease was enough to
prevent an additional dynamic one from being created.

Thanks for any help.