Two NetInstall/NetBoot Server

Hello,

i have a NetBoot Server for diagnostic purpose in my network, works great. Now i would like to setup a MacMini with two ethernet interfaces (built-in and USB-Interface) to use it for NetInstall and make a own subnet.

The Setup looks like this.

en0 (bulit in) has got a static IP Adress in the network and can access the internet (192.168.80.11)

en4 (USB-Ethernet) is running DHCP Server and Netinstall (192.168.70.0/24) -> Netboot works but Clients have no internet acces (tried different DNS settings)

If i turn on Internet sharing, the second interface is not available anymore for NetInstall so that is no solution?

Anyone got a setup like this and knows how to get it running?