Network topology = Network Diagram
So if the SBD router is the RUT240 meaning the connection from the Firewall to the devices of RUT240 is established right? But what you want is the devices A, B, and C will be able to communicate with the devices connected on the firewall side? Is that correct? If I am wrong could you sketch a network diagram that is having to address samples and illustrate what you are trying to do? For me to guide you more efficiently.
I hope it helps.