Internet only works through router...

[lilblam]

Here'd the deal:

I have 2 computers, a MAC and a PC sharing a Comcast cable broadband connection via a Netgear router. My problem is (short version), when I unplug my PC from the router, and connect it directly to the cable modem, the connection doesn't work any longer as the PC doesn't seem to DETECT the cable modem. It did work before when I did this (few months ago), but now the internet only works via the router!

Here are the details:

As soon as I unplug the PC from the router, WinXP informs me that my "Network Cable is Unplugged" in systray. When I plug it into the cable modem, the modem detects my PC because the "PC LIGHT" goes on. However, the PC has its own network light on the network card, when it is plugged into the router and the connection works, the light is green. When I plug the PC directly into the cable modem, the light is orange (indicating that the connection isn't working).

The odd thing is, the cable modem does see the PC, but the PC doesn't see the cable modem, and even after I plug it in directly, it still thinks that "Network Cable is Unplugged".

Any suggestions on what might becausing this and what I could do to fix it?
---------------------------------

Additional info:

Comcast customer support won't trouble shoot a PC that's connected via a router. My connection has been slow lately (1.7Mb/s instead of the promised 3.0Mb/s), that's why I want to troubleshoot it. When they asked me to plug the PC directly into the cable modem so they can check the signal levels etc, I realised that that setup no longer works for some reason, so now I have a new problem. :)

CPU: Pentium IV (Willamette) 1.6Ghz (400Mhz FSB), Compaq Presario 5000 series
RAM: 512MB (Micron Technology, DDR-SDRAM PC2100)
Motherboard: Intel, Chipset i845D
OS: Windows XP Home, SP1
Influential Software Running: ZoneAlarm PRO firewall, Norton Antivirus.


Any and all help is appreciated.

-Mike

[johnwill]

Power cycle the cable modem when you change the attached devices. That's a normal problem if you don't.

[lilblam]

Hey John,

I did. I disconnected the modem for 2 minutes and reconnected it (after it was already plugged into the PC). The problem persists.

I think it's on the side of the PC, because the PC doesn't even detect a connection when it's plugged in to the cable modem directly - it still thinks the network cable is unplugged for some reason. The modem does see the PC, however.

What could cause the PC to only detect the router when it's connected to it, but not the cable modem?

[Volt-Schwibe]

this is a little far out, but you might check it with a different cable.

sometimes, the pins in the end of the cable are sorta smashed in, and it doesnt touch all the way.

and, to make it worse, sometimes, the cable works fine when connected to one pair of devices, but doesnt work when connected to a different pair of devices.

[johnwill]

Your router may also be using a cross-over cable, I ran across one of those several years ago, took me about an hour to figure out it needed a non-standard cable! If so, you'd need a crossover cable for the standard NIC on the PC. Read the manual...

I'm betting that Waltside is right and it's just the cable.

One other possibility, it may be an incompatibility between the NIC and the modem. I've had that happen a couple of times, and a cheap hub/router in between made them work.

This is what makes computers fun!

[Volt-Schwibe]

Originally Posted by johnwill

This is what makes computers fun!

yes, it is :)

[lilblam]

Thanks for your replies guys,

I highly doubt it is the cable for the simple reason that it worked before with that cable. About 5-6 months ago it worked fine, NIC directly to cable modem. I have the exact cable I used, and a few others just like it (I tried different ones just in case). This time, they all do not work. I might ask Comcast about this, it's always possible that they changed something on their end...

Here's another curious fact. The Mac I have does work when plugged in directly into the cable modem. It's the PC that doesn't recognize it for some reason. If anyone has any further suggestions, I'm all ears :)

[stretch001]

its your default gateway adress my freind, i bet you pc is still looking for your router as its gatway!

right click on MY NETWORK PLACES
PROPERTIES
double click on LOCAL AREA CONNECTION
Double click on INTERNET PROTOCOL

remove your default gateway adress, this will be the addressof your router,somting like 10.0.0.2 i guess.

now try it

[lilblam]

Well, in the configuration settings it says "Obtain IP Address automatically", which includes IP/subnet mask/default gateway together. When I look at what my default gateway is by typing "ipconfig" in command prompt, it says "127.0.0.1". That is the default address of my router as well. But shouldn't it automatically change when I plug in my cable modem instead? It must've done this before when it did work...

I even tried going to router settings, checking all the info it got from the ISP (the actual gateway the ISP uses for example) and typed that in my Internet Protocol properties and then tried to connect it to the cable modem. Still nothing. Keeps saying "network cable is unplugged". It would make more sense if it at least realised that network cable is plugged IN, and then just didn't work.

beh :o

[johnwill]

Well, that's certainly a problem! 127.0.0.1 is your loopback address, and that sure doesn't belong in the default gateway slot! Try these fixes in this order.

WINSOCK Fix XP: http://www.spychecker.com/program/winsockxpfix.html

Reset TCP/IP Stack: http://support.microsoft.com/default...&Product=winxp

[lilblam]

Ah crap I put the wrong ip, sorry.

I said my default gateway was 127.0.0.1

Actually, it is 192.168.0.1 - which is also the IP of my router. Had the 2 IP's mixed up in my mind, sorry about that.

[lilblam]

I fixed it!!

Here's what I did to fix the problem

1) I went to NETWORK CONNECTIONS.
2) Right click on LOCAL AREA CONNECTION to go to its properties
3) Click CONFIGURE to configure the Network Card.
4) Go to ADVANCED
5) On the left list of options, click on LINK SPEED & DUPLEX

There it was originally set on "100Mbps/Full Duplex".

I changed that to "AUTO DETECT".

Bam, problem solved. Here is where I found the general steps for this solution, but improvise a little bit:

http://www.experts-exchange.com/Netw..._20418688.html

Thanks for all your help guys, you learn something new every day :)

Now my question (which I'll probably research myself) would be, why did that fix the problem? Knowing how without the why can be foolish :)

-Mike

[Volt-Schwibe]

ok, i'm not the professional here, but the fact that you had to set it to auto detect instead of 100mb/full duplex tells me that your configuration is having a problem with 100mb/full, and is having to run in 10mb, or half mode, or both.

so, something is not optimal, but working is better than not working.

[johnwill]

I think WaltSide may be onto something, I'd check the cables...