Install Mac OS X via network across different subnets

We have more than 70 subnets and lots of switches. I want to install Mac OS X to client computers. By the way the computer may have an operating system installed or not. I want to put an Apple Server in one place and all clients install Mac OS X from there. In the local network everything is fine but in a different subnet net install does not work. I searched some techniques but I think they are not for us. For example my Mac OS server's IP is 10.10.4.40 and the destination computer's IP is 10.10.12.23 Also our switches' configs are fine for netboot/netinstall (portfast and etc.) But our technicians says "Computer cannot see the OS X Server". I also read bootpd, Apple shell script solution vs. but the main problem is destination computer may not have operating system. Please give me easy way to do it.