Using a Hub to hook into a Cable Modem --CDU often times doesn't work...your ISP assignes you ONE IP address...but their server will see several MAC (physical) addresses from you....making its poor server confused...

Try with one PC hooked up to the CDU..if it works, pick up a router or switch to run multible PC's behind the CDU.

You can run a hub BEHIND the router/switch if you desire...

I can get in the differances between a router, switch, bridge & hubs if you desire.