Perhaps I am misreading your response, if I am, I apologize.
From what I read your problem was that Drobo Dashboard (on your computer) couldn’t “see” your Drobo FS.
Unless the two are on different networks, or you have a very high-end (i.e., not SOHO) router, both your FS and your computer are both on the LAN side of the router, and effectively their communication is like they are on the same switch.
The router settings commonly called port forwarding and port triggering are for allowing traffic between the WAN and LAN sides of the router. Since both devices are on the LAN side, and as you said your router does not have a firewall function. This is also why, as you said, your router configuration only allowed for the ports to go to one device (your Drobo FS or your laptop), because essentially the router is “connecting” its WAN IP address and port to a LAN IP address and port. That’s why it’s a one-to-one relationship.
Again, that has nothing to do with LAN-to-LAN communications though.
The KB article, inaccuracies and all, is written in reference to the computer/workstation’s built-in Firewall (XP/Vista/Win7 Firewall, for example). You can tell this from the reference to “allowed program list” - a router as a strictly-network device only knows about traffic, not about what program is generating that traffic. Some traffic is program-specific, but it wouldn’t be able to say something like “Allow FTP traffic from CuteFTP, but not from WS_FTP” - only the computer running those applications would know which one is generating what traffic.
Regardless, happy you got things working, but I still recommend un-doing the router changes.
Now, if you are trying to make your FS accessible from a device on the WAN side (any random Internet address), then it’s a different story…