I experienced this problem as well. However it is slightly different, but might point you to the fix. I have a Dude agent running on a remotely monitored network. Everything worked fine except the RouterOS data wasnt showing up. Having exploited EOIP to great benefit before, I had a wild idea. I created an EOIP tunnel directly to the Dude on ROS on X86 machine. The tunnel endpoints were on the 'gateway' MT radio running the Dude agent, and on the Dude machine. This is another advantage of Dude on ROS. By creating that tunnel to pass data directly to the Dude on the correct subnet, it immediately delivered all RouterOS data to the Dude server and displays very reliably. On top of that, the 333 running the agent was also running NAT for the HotSpot I had running on the second wireless NIC. Therefore, that nifty proprietary EOIP tunnel just poked a hole right through NAT, directly to the Dude server. I thought the 333 would choke running the Dude, the Hotspot, two mini-PCI NICS and passing significant traffic. The only available routerboard I had on me was a 333, so I had to try it, and its just idling along at about 5-25% CPU utilization, with 35.7MB RAM free, and 18.5MB HDD free. Pretty efficient I must say, even though the direct access to the Dude server in the 333 is slow. Still get 20Mbps throughput to boot.
So the moral of the story is that the Dude server must be able to directly communicate with the remote network, even though the agent is already directly connected. SNMP doesnt have this problem. I would look into any router, NAT, or especially firewall transversal because it seems to be a one-way street. Now that I think about it, the EOIP tunnel would actually allow the main Dude server to monitor the remote network. That is of course if your customer doesnt consider this a breach of security. On-the-ball network administrators should be asking 'where are those unknown IPs and MACs located? Word to the wise...
The agent is still my preferred solution because it can be configured to be quite transparent to probing network administrators that have nothing better to do...Personnel at one of these agent locations still are oblivious to the fact that I can tell them what is down on their network, even though I am not anywhere close to their network and have never thought to ask me 'How
did you know that?'.
Stealth is good...