RDM understanding

On the Element, In the Shell, On the Network Page, Under Interfaces, for the Network Card you are using, make sure that RDM is enabled.

Also, while you are in the Shell, you can go to the Maintenance Page, then Launch Concert and perform a Network Map.  If RDM is configured properly in the rest of the system then you should see the fixtures show up connected to the Gateway.  This will confirm if it is an Eos setting issue or a larger issue.

yep its set up like that

but i did not have to do anything for the other Element.  no concert or mapping.  I have the other element plugged into a Ethernet hub, and my spare NET3 node into that and the Luster into the port 1 output configured as universe 2 and the RDM works fine

The Concert part is to test to confirm if the Element (as a computer) is connecting to the Gateway and getting the RDM traffic outside of the Eos/Element OS.

Based on your two comments you "Backup" Element can see (over RDM) the Fixture either through the Local DMX port or over a network and Gateway?  If I understand you correctly, this is not the same network as the "Primary" Element - is that correct?

The Concert part is to test to confirm if the Element (as a computer) is connecting to the Gateway and getting the RDM traffic outside of the Eos/Element OS.

Based on your two comments you "Backup" Element can see (over RDM) the Fixture either through the Local DMX port or over a network and Gateway?  If I understand you correctly, this is not the same network as the "Primary" Element - is that correct?

correct.  the backup is just another Element in our shop.