WDM PXE Imaging behind router

Hello everyone,

We’re running a small WDM 5.7.2 on Windows Server 2008 R2 with PXE Imaging for the D90D7 Clients. Some Clients still got an old boot Agent 2.7.3

We got these subnets:

192.168.10.0/24 - WDM-Server / First DHCP-Server / Lots of clients

192.168.11.0/24 - No Servers

192.168.12.0/24 - Second DHCP-Server

192.168.13.0/24 - No Servers

All subnets are connected by a dirk fiber and routers. Now we have big problems with the PXE Imaging. It seems our clients from the second DHCP-Server are unable to communicate with the WDM while booting the pxe.

Has anyone experience with these problem?
Best regards
Chris