Please will you be kind enough to elaborate on your suggestion for an alternative way of me sniffing everything to and from the NAS.
I'll endeavour to return a little later with some more detail..... just trying to see if I can find a diagram that will do the job of a thousand words first, or at least a paragraph or two of words !
PS - I have two gigabit LAN ports in the PC I will run the sniff from but believe they relate to one physical card.
Wouldn't worry about that too much ... anything in your PC becomes a managed switch (not the correct word, but contextually appropriate !)..... if it's anything like macs or servers then you'll probably find it's not even a network card but just coming off the motherboard ....