So after trying all the above step you are still having issue? Have you try talking with networking to configure the router IP helper table
For a PXE server to respond to a PXE request, the request must be able to transverse routers to communicate with PXE servers on other subnets. PXE uses the DHCP option fields to pass information. Therefore having the PXE server in the routers IP helper table helps make sure that the DHCP packets are forwarded to the PXE server so the PXE server can respond correctly.
To resolve this issue, you must remove these options from the DHCP server and configure the routers IP helper table to contain the IP address of the RIS server.
You can also optionally create a provisioning boot media cd, boot off the cd and kick off your osd capture script from it.