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Wired connection to cable modem not working, wireless router working just fine

Frequent Visitor

Wired connection to cable modem not working, wireless router working just fine

Hello, my networking setup has been working fine for nearly two years, but yesterday, it spontaneously stopped working.  Here's my typical setup:

 

1) Arris touchstone tm502g/ct - the comcast unit

2) a pretty old ZyXEL P334W/T wireless router.  It has 4 lan ports.

 

So I had the modem connected via cat5 to the router; I have a laptop, a kindle, and a galaxy 2 that all connect wirelessly through the router.  I had one of the lan ports connected to my desktop.  As I mentioned, this was all working fine until yesterday.

 

Now the wireless connection still works, but I'm unable to connect through the lan port on the router.  

 

0) I verified the internet settings on my desktop to ensure it's using dhcp.

1) I've reset the modem and router many times.  

2) I've changed the lan port and reset the modem and router

3) I called comcast support and they reset the modem remotely

4) I've rebooted my computer many times

5) I've tried connecting the modem directly to my desktop via cat5

6) I've tried connecting the modem directly to my laptop via cat5

 

Thinking creatively, I tried sharing the wireless connection on my laptop with the local area network.  I plugged the desktop into the laptop via cat5 and that's not working.

 

Another interesting thing - I live in a building with shared internet access via another wireless router.  On my notebook, I've tried connecting to that wireless network and the same trick of sharing the wireless connection via the local area network.  That's not working.

 

I've tried changing the cat5 cable, but that didn't make a difference.

 

The other interesting thing, when connected wirelessly to the router, I can access the gateway web interface at 192.168.1.1; when my desktop is connected to the lan port, I can not access the gateway web interface.

 

One last thing, when I plug the modem into the desktop, I'm not able to reach any addresses.  I tried to ping 8.8.8.8 & 8.8.4.4 (google public dns servers) with cygwin ping, but I couldn't reach them.  The error message was meaningless "transmit failed.  General failure."  I was thinking maybe it was a DNS issue and I could force the wired connection to use google public dns, but no luck.  Also, please note I verified that my local area network connection was correctly set to use dhcp (including name servers) and did not change that.  I only tried pinging the google servers.

 

Really puzzling.  If it's a modem issue, why does the wireless router work?  If it's bad lan ports on the router, why doesn't it work when I plug the modem directly into the desktop?  If the NIC doesn't work on the desktop, why doesn't it work when I plug the modem directly into the laptop?

 

Thanks in advance - 

 

-Matt

Frequent Visitor

Re: Wired connection to cable modem not working, wireless router working just fine

I replaced the modem and am having all of the same results whether connecting to my wireless router, through which my laptop can connect to the internet wirelessly but not my wired desktop, or whether I connect the modem directly to either my desktop or my laptop.

 

I'm not enough of a network engineer to understand what's going on under the hood.  But it really seems like the router is either oblivious to some setting coming from the modem that's preventing the laptop or desktop from connecting, or the router is more savvy to some setting coming from the modem.  It's really inexplicable to me that I can't get internet access when I wire the router directly to my laptop or desktop.

 

I've checked and rechecked local area network settings on both the pc and laptop.  I've checked the LAN, WAN, and firewall settings on my router.  Those wouldn't matter if I connected directly from the modem to the laptop or desktop.  I reiterate that I didn't change any settngs.  All was working fine with me until 7:45 PM GMT-7 on Tuesday, then all this started.

 

Both the desktop and the laptop run windows 7 pro 64 bit.  I dual boot the desktop with ubuntu, however, and I won't get into how that doesn't work, but suffice it to say, it can't connect to the internet either.  Also I think if Microsoft pushed an update that prevented me from connecting to the internet, there would be a hew and cry.  Although it may go unheard since none of us are able to connect to the internet.

Problem Solver

Re: Wired connection to cable modem not working, wireless router working just fine

EVERY time you change what is connected to a modem you MUST turn it off.  If it has a battery the battery must also be disconnected.

 

Expert

Re: Wired connection to cable modem not working, wireless router working just fine

FWIW, unless it's malfunctioning, one could also use the recessed reset button on the rear if they don't know how to take the battery out.

Frequent Visitor

Re: Wired connection to cable modem not working, wireless router working just fine

I have tried many different permutations, most frequently I would:

 

1) shut down the desktop

2) connect the modem to the desktop

3) reset the modem with the indicated reset button.  The lights would all go out except the power indicator.  I'd wait until they all came back on (except the network indicator)

4) power on the pc.  I'd see the network indicator on the modem flash, and I saw the network activity indicator on the ethernet port on the pc, but windows was showing no internet connection.

 

As I mentioned above, I could try pinging known ip addresses, e.g., 8.8.8.8 and it failed with the unhelpful 'general failure' message.

 

So then I could take the cable from the pc and connect it to the router.  I could connect wirelessly to the internet through the router on the laptop without resetting the modem.

Problem Solver

Re: Wired connection to cable modem not working, wireless router working just fine


kazaak wrote:

So then I could take the cable from the pc and connect it to the router.  I could connect wirelessly to the internet through the router on the laptop without resetting the modem.


That means that the modem was not reset.  A modem remembers the first MAC address it receives after reset and will block all other MAC addresses from connecting.  That's how Comcast prevents you from getting more than one IP address from them.

 

Frequent Visitor

Re: Wired connection to cable modem not working, wireless router working just fine

Ok, maybe I'm missing something?  I don't know how to reset the modem other than using the reset button on the modem in the method I described above, which I'll repeat.  I have a contrivance (a toothpick, it happens) I stick in there.  I watch the lights on the front to ensure that they all go out (again, as I described above, all the lights except the one power indicator).  After doing this, I watch the lights come back on one at a time.  Is there another way to reset the modem?  There's no way for me to disable the battery otherwise, is there?

 

 

 

Expert

Re: Wired connection to cable modem not working, wireless router working just fine


kazaak wrote:

 

Is there another way to reset the modem?  There's no way for me to disable the battery otherwise, is there?

 


As stated, If the reset button doesn't seem to be functioning, you need to unplug the modem from the A.C. power outlet and also remove the battery from it's compartment and try waiting for five minutes for a full hard reset.

Frequent Visitor

Re: Wired connection to cable modem not working, wireless router working just fine


EG wrote:

As stated, If the reset button doesn't seem to be functioning, you need to unplug the modem from the A.C. power outlet and also remove the battery from it's compartment and try waiting for five minutes for a full hard reset.


Ok, I'm with you.  Thanks for the responses.  First I tried to get the router working:

 

1) disconnected power from the router, shutting it off

2) disconnected the router from my desktop

3) pulled the plug on the modem

4) removed the battery from the modem

5) wait 5 minutes in calm meditation and reflection until my attention span waned and I started wondering if my deodorant was still working

6) verify local area network settings on desktop set to use dhcp.

7) shut down the desktop

8) plug in the modem

9) put the battery in the modem

10) watch the lights come back on until they are all on except the network activity light

11) plug in the router.  Watch the lights come back on, including wan activity on the router and flickering network activity on the modem.

12) plug the router back in to my desktop, which is still powered down

13) power on the desktop

 

Unfortunately, this yielded the same result.  I was able to connect from the laptop wirelessly via the router, but the desktop shows no connection to internet.  I'm unable to ping 8.8.8.8 and I can't reach the router's web interface at 192.168.1.1.

 

My second test, I wanted to take the router out of the equation and connect the modem to the desktop:

 

1) disconnected the modem from the router

2) pulled the battery from the modem

3) unplugged the modem

4) disconnected my desktop from the router

5) wait 5 minutes, surmising my deodorant would hold

6) shut down my desktop.  At this point the modem is not connected to it

7) put the battery back in the modem

8) plug in the modem

9) wait for lights to come back on on the modem, except network activity

10) connect the modem to the desktop

11) power on the desktop

 

Still the same result.  I can see the network activity light flashing on the desktop, and I can see same flashing on the modem.  Watching the network status, I can see packets sent but none received.  The windows 7 diagnostics tool makes a reasonable guess to disable and then reenable the connection, but that doesn't resolve the problem either.

 

I don't want to go through this exercise with my laptop at this point.  It's been ages since I've plugged a cable into it, so I suppose it's possible the NIC doesn't work on it.  The NIC on the desktop is an onboard controller on a gigabyte mainboard.  I'm going to try throwing a card in the desktop to see if that helps.  Thanks again.

 

-Matt

New Poster

Re: Wired connection to cable modem not working, wireless router working just fine

My brother is having this exact problem. I'm dumbfounded trying to help him over the phone. Wired connection doesn't work if it's coming directly from the modem, or the router. However.. when the router is hooked up he can access it wirelessly. It's so odd. Have tried all hard resets/reboots/battery&power removal... Comcast signals reset etc. No luck.

Was this problem you were having ever resolved? Comcast tech support is being little to no help as usual. He told me one call the rep told him his router was the ussue, when it was never connected the entire phone call. When told the router wasn't even in series with any of their equipment, he just hung up. Any help or nudge in the right direction would be very much appreciated.

Thanks!
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Re: Wired connection to cable modem not working, wireless router working just fine