Hi Gary,

Thanks for replying. This had certainly baffled us. So much so we went to site last night to see for ourselves what was happening during the backup window.
To cut a long story short we discovered that the 5 x 48 port switch fabric that is connected via the cascaded ports had 3 ports in switch #1 patched directly to 3 ports in switch #2 and Spanning Tree was disabled.
I guess this would explain why other devices appeared in the graph.
I will email you the workspace file prior to our visit.

Many Thanks
Graham