Router connection OK but Modem Connection fail

[sylvesterk]

Can someone explain why I couldn't get my OBI202 to work when I connect it directly to my Motorola Cable Modem SB6120. It works when I connect it to via a Cisco router?

I wanted to have it connected to my Modem directly and then connect the Lan port to my Cisco router. This way I can turn off my Cisco router when I am not not home or at night while my Obi202 and modem stay on all the time. Thanks

[pc44]

Hi sylvesterk,

Have you tried *resetting* your Cable Modem when switching between your Router and your OBi202?  Due to some MAC binding issues with cable modems, this may be necessary and/or helpful in your situation.

Hope you get it working,
pc44

[Rick]

Can someone explain why I couldn't get my OBI202 to work when I connect it directly to my Motorola Cable Modem SB6120. It works when I connect it to via a Cisco router?

I wanted to have it connected to my Modem directly and then connect the Lan port to my Cisco router. This way I can turn off my Cisco router when I am not not home or at night while my Obi202 and modem stay on all the time. Thanks

I suggest you are wasting your time on an effort that has very little savings.  Check the power requirements of your Cisco router, and do the math as to how much that costs a month.  Weigh that against hiding your OBi behind your router vs. exposing it more to the internet. 

[sylvesterk]

Actually, I am not trying to save power but just to protect my router so that it won't go bad too soon.

However, after couple of trial and error, I succeeded in getting it to work the setup I wanted.
Basically, it was the sequence that I turned on those hardware making the difference.

It will not work if I turn on all the hardware  at the same time. It will only work by turning the Modem power on first and let it run fully follow by the other two.  If the modem did  not run fully or to soon to turn on Obihai and router, it will not work either.

[geva]

A device being plugged into a cable modem requests an IP address from your ISP.  Typically this device would be a computer or a router.  Also typically, cable providers only allow you to have one IP address at a time, meaning that you cannot have multiple computers plugged into the modem surfing the web at once.  Using a router is how most people get around this limitation.  It is possible however that the cable provider will allow you to have more than one IP address, so the router and the OBi would both be able to be plugged in.

It is also possible that both the router and the OBi think that they have the same IP address.  Although this may work... there would be inherent problems leading to communications screw ups.

I wouldn't worry about the life of the cisco router if I were you.  It should easily last 10 years.  Just make sure that it is cooled properly (as in not over heating).  Many would argue that turning the solid state router on and off thousands of time (2 times a day, for multiple years) would be way harder on it than leaving it on all the time.  Keep in mind that routers are designed and tested to be running all the time; not continually power cycled.