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So, I have a router that is plugged into my cable modem. I was getting connectivity issues, so I plugged my machine directly into the modem to find out which was the weak link. I could get connectivity plugged directly into the modem, so I figured it was the router. So, I bought a new router and I still have the same issue. Does anyone have any thoughts as to why I could get connectivity plugged directly into the modem, but not plugged into the router when it is plugged into the modem? Thanks.

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migrated from Jun 27 '10 at 5:45

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More info: router brand/model, computer OS, modem brand/model – hyperslug Jun 27 '10 at 6:06

Here are some guesses:

  • The cable modem is looking for your computer's MAC address only. The router needs to spoof that MAC.
  • The cable modem needs to be power cycled after the router is on and booted for the cable modem to connect.
  • The wireless network is not working, either on your computer or on your router.
  • The router is configured improperly for NAT.
  • One of the patch cables you are using is defective.
  • Both routers were defective from the factory.

Try connecting modem -> router -> computer and logging into the router to see if it receives a WAN address from the modem. For example, a Linksys modem has a Status page that can indicate it is receiving a connection from the modem:

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Cable co locking down to MAC seems to be going away, but even if they're not filtering that way anymore I've found that rebooting the cable modem is often required (despite the big warning stickers on them that say "never unplug power from this device"). – Brian Knoblauch Aug 17 '10 at 17:02

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