I found this
on this page after googling your router:
Does anyone know how to port forward the Motorola SurfBoard SB5100 Cable Modem? I can't find any guide in the net for this modem. I'm using Telstra Bigpond cable internet, help please.....
There is no firewall or router in the Motorola sb5100. It's just a modem and that's it. There is no ports to open up, or to forward.
And
this page seems to confirm it (read the whole thread, not just the beginning).
So, what OS are you using? And what bt client? And what makes you think you are firewalled?
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