Welcome to Comcast Help & Support Forums
Find solutions, share knowledge, and get answers from customers and experts

New to the Community? Start here.

5,495,623

members

18

online now

1,702,443

discussions

SOLVED - router/laptop works from one cable modem not another

Posted by
Edited on
‎04-17-2011 10:26 PM

Visitor
  • Thank you contributor for your first reply to the community!
 Posting replies is the best way to get involved.
  • Congrats on Posting your first topic!

Member Since: ‎07-25-2009
Posts: 3
Message 1 of 6 (1,146 Views)

SOLVED - router/laptop works from one cable modem not another

[ Edited ]

The initial problem

A friend of mine (also on Comcast) was having trouble with a netgear router being flakey and getting knocked off wireless periodically.  Since she lived in an apartment complex and I saw many other wireless routers on the same channel I aimed to change the wireless channel.  Dell laptop running Windows XP was slow but otherwise functional on a wireless connection.

 

Couldn't Get into admin on router

Password unknown.  Since this was going to take a reset and she also had some problems with the laptop, I took the router aand laptop back to my place.

 

Setup the Router again and plugged into my Comcast modem. 

Everything works now, wireless, wired etc.  After a little work on the laptop things are working nicely.  Power cycled and everything is still good.

 

Brought everything back, plugged into her Comcast modem - Problems!!!

Laptop connects wirelessly, or via ethernet, however no internet access.  Browser acted as if there was no DNS however an ipconfig /all showed dns assignements.

Unplugged router and plugged laptop directly into the cable modem with an ethernet cable... everything works!

 

I'm stumped.  Have never seen anything like this before.  I have the feeling i'm missing something really simple and stupid here but what?  Is there some issue with the modem that makes it not want to talk to the router?

 

Ideas?

 

Rich

5 REPLIES
Posted by
Edited on
‎04-12-2011 04:00 PM

Connection Expert

Member Since: ‎12-24-2003
Posts: 51,648
Message 2 of 6 (1,144 Views)

Re: Geek Challenge: I'm stumped - router/laptop works from one cable modem not anothe

[ Edited ]

Are you properly powercycling the modems each and every time that you are changing the devices that are being connected directly to them ?




Community Icon
I am not a Comcast employee, I am a paying customer just like you! I am an XFINITY Forum Expert and I am here to help.To learn more about XFINITY Forum Expert program click here.
Was your question answered? Mark it as an accepted solution!solution Icon
Did this post help? Why not give it a kudo!!!Kudos Icon
Community Icon
I am not a Comcast employee, I am a paying customer just like you! I am an XFINITY Forum Expert and I am here to help.To learn more about XFINITY Forum Expert program click here.
Community Icon
I am an XFINITY Forum Expert and I am here to help. Expert Program
Posted by
Visitor
  • Thank you contributor for your first reply to the community!
 Posting replies is the best way to get involved.
  • Congrats on Posting your first topic!

Member Since: ‎07-25-2009
Posts: 3
Message 3 of 6 (1,139 Views)

Re: Geek Challenge: I'm stumped - router/laptop works from one cable modem not anothe

Tried removing power to the modem, but this is designed to service phones as well and removing power doesn't seem to deenergize anything.  Battery backup? 

 

The only way to reset the modem is to call comcast and ask for a modem reset over the phone.  I did try that by the way but it didn't help.  But again the modem works directly connected to the laptop.

 

Never seen a problem like this before.

Posted by
Connection Expert

Member Since: ‎12-24-2003
Posts: 51,648
Message 4 of 6 (1,135 Views)

Re: Geek Challenge: I'm stumped - router/laptop works from one cable modem not anothe

Yes. If you are using a telephony type modem that has a built in backup battery then just removing the A.C. power will not powercycle it. You need to use the recessed reset button on the rear. You'll need something like a bent paper clip or the tip of a pen to do so. Alternately you can both remove the battery and the A.C. power to reset it. 




Community Icon
I am not a Comcast employee, I am a paying customer just like you! I am an XFINITY Forum Expert and I am here to help.To learn more about XFINITY Forum Expert program click here.
Was your question answered? Mark it as an accepted solution!solution Icon
Did this post help? Why not give it a kudo!!!Kudos Icon
Community Icon
I am not a Comcast employee, I am a paying customer just like you! I am an XFINITY Forum Expert and I am here to help.To learn more about XFINITY Forum Expert program click here.
Community Icon
I am an XFINITY Forum Expert and I am here to help. Expert Program
Posted by
Visitor
  • Thank you contributor for your first reply to the community!
 Posting replies is the best way to get involved.
  • Congrats on Posting your first topic!

Member Since: ‎07-25-2009
Posts: 3
Message 5 of 6 (1,088 Views)

Re: Geek Challenge: I'm stumped - router/laptop works from one cable modem not anothe

That did it.  Thanks. I'm surprised the modem is that sensitive.  Not sure why it wasn't needed when I plugged into mine though. 

Posted by
Edited on
‎04-17-2011 11:10 PM

Connection Expert

Member Since: ‎12-24-2003
Posts: 51,648
Message 6 of 6 (1,083 Views)

Re: Geek Challenge: I'm stumped - router/laptop works from one cable modem not anothe

[ Edited ]

Glad that worked for you ! It's not that it is "sensitive". The modem stores the hardware MAC (Media Access Control) address of the last device that was directly connected to it. It is deliberate that it has a MAC address cache that can only be cleared via a powercycle operation. CC supplies only a single IP address to a residential connection.




Community Icon
I am not a Comcast employee, I am a paying customer just like you! I am an XFINITY Forum Expert and I am here to help.To learn more about XFINITY Forum Expert program click here.
Was your question answered? Mark it as an accepted solution!solution Icon
Did this post help? Why not give it a kudo!!!Kudos Icon
Community Icon
I am not a Comcast employee, I am a paying customer just like you! I am an XFINITY Forum Expert and I am here to help.To learn more about XFINITY Forum Expert program click here.
Community Icon
I am an XFINITY Forum Expert and I am here to help. Expert Program