I cannot draw a valid IP address.

[Frank12345]

Hello everyone.  This forum was recommended to me by a friend. 

I am going insane because of this problem.  I have spent countless hours trying to fix this.  Dell and comcast were equally worthless. 

I have a two computer network, both wired to a router which is wired to the cable modem. Both computers run windows XP.   

Upon returning home last week, neither computer would connect to the internet.  After some attempts at troubleshooting, this is the current situation:

Scenario 1 - Both computers connected to the router -

Neither computer connects to the internet, but my home network is functioning.  I can transfer files from my main computer to my secondary computer, and I can print from the secondary computer using the printer attached to the main computer.

Oddly enough though, the secondary computer pings the main computer, but the main computer times out when pinging the secondary computer.

Scenario 2 - Main computer wired directly to the cable modem:

This will not work at all, no matter what I do.  I need to get this computer connected to the internet!  It draws a 169 IP address and will NOT draw a valid one no matter what.

Scenario 3 -  Secondary computer wired directly to the cable modem:

This works, drawing a valid IP address.  However this computer is a 7 year old piece of crap and I am slowly going insane trying to use it for my primary activities.

Scenario 4 - Secondary computer hooked up to router but without main computer hooked up at all:

This does not work.  I don't understand.  In scenario 2, the main computer is failing and the router is not involved at all.  In Scenario 4, the router is failing while the main computer is not involved at all.  Yet the Router works in scenario 1 for my local network.  I am absolutely stumped.  Everything worked fine, and then upon turning on all components the next day, I seem to have two pieces of equipment failing.

Solutions I have attempted:

1)  Power cycling everything, swapping cords and cables, etc.

2)  entering the IP and DNS info manually on the main computer to match the valid data from the secondary computer. 

3)  Used VB winsock fix on the main computer.

4)   Wasted a lot of time with comcast technicians.

I am out of ides.  Please help.   Thanks.

[Allan]

If neither computer has access to the internet when connected directly to the modem, either the modem is bad or the problem is most likely on Comcast's end.

[Frank12345]

If neither computer has access to the internet when connected directly to the modem, either the modem is bad or the problem is most likely on Comcast's end.

Agreed.  However, as seen in my explanation of scenario 3, the cable modem is working and the secondary computer can connect to the internet.  I will revise the original post to make it more clear, my apologies for any confusion.

It seems I can no longer edit my first post.  But in Scenario 3, where I have the secondary computer hooked directly to the cable modem, I can access the internet.  But if I try to hook up either the router (without the main computer) or if I try to hook the main computer directly to the modem, I get no internet access. 


I cannot seem to isolate the problem to a specific piece of equipment. 

[Allan]

Okay, sorry. Your first post was a little lengthy and I admit I skimmed through it.

1) Let's start at the beginning. If you connect your "primary" computer directly to the modem it does not work, correct? Did it ever work? If so, what happened between the last time it worked properly and the first time it did not (new hw, sw, virus, error, etc)?

2) Did you try a different NIC in the computer?

3) Did you try safe mode with networking? If not, please do.

[Frank12345]

Okay, sorry. Your first post was a little lengthy and I admit I skimmed through it.

1) Let's start at the beginning. If you connect your "primary" computer directly to the modem it does not work, correct? Did it ever work? If so, what happened between the last time it worked properly and the first time it did not (new hw, sw, virus, error, etc)?

2) Did you try a different NIC in the computer?

3) Did you try safe mode with networking? If not, please do.

1)  It did work.  The last time it was on right before it failed, it was working fine.  As for what happened between the last time it worked and the first time it failed - Nothing happened.  No changes, nothing.  These facts are what is most baffling about this. 

2)  No.  Much to my annoyance, both models have the network port build right into the motherboard.  There is no removable NIC in either one.

3)  I have not tried this but I will. 

But all of this focuses on the main computer.  Even if that is fixed, why won't the secondary computer work when connected to the router?  I swear some gremlin broke in and tinkered with my equipment just to screw with my head.

[Allan]

Do you have a nic you can try in the system?

[Frank12345]

I don't.  But I can go pick one up to see if that solves the problem.

[Allan]

Worth a shot. You can always return it.

[Frank12345]

This failed as well.  Everything is the same as it was with the original NIC.  And as with the original NIC, the device manager says the card is working properly. 

I am out of ideas. 

[midsail]

Try this simple trouble shooting steps on each computer.
open a command prompt.
1- ping 127.0.0.1 this is a loop back test. All this does is tell us if the SW is OK or corrupt.
2- ping the IP Address of the computer that can get an IP. This will let us know if the NIC is bad or not.
3- ping the gateway IP address.
If I understand correctly. Both computers can communicate in the intranet? It might be that the gateway IP address has change somehow. If u can not ping the gateway IP Address it has to be the modem/router.

[ale52]

What do you get for the default gateway with the      ipconfig /all   command?

Alan <>< 

[Frank12345]

Try this simple trouble shooting steps on each computer.
open a command prompt.
1- ping 127.0.0.1 this is a loop back test. All this does is tell us if the SW is OK or corrupt.
2- ping the IP Address of the computer that can get an IP. This will let us know if the NIC is bad or not.
3- ping the gateway IP address.
If I understand correctly. Both computers can communicate in the intranet? It might be that the gateway IP address has change somehow. If u can not ping the gateway IP Address it has to be the modem/router.

Thank you for the reply.  What makes this difficult is that (using direct connection to the cable modem) one computer will connect to the internet and one will not.  But the one that connects to the internet will only do so if I remove the router, so I have to keep hooking and unhooking things to try these various different tests.   

When hooked up to the router, I can send files from one to the other but neither can connect to the internet.  Oddly, one can ping the other, but not vice versa (!?). 

[Frank12345]

Okay.  Here is what is happening.  With the old computer hooked up to the cable modem, I get valid IP numbers and everything works.  I then hooked up the router to the cable modem and hooked both computers up to the router.  When I run IPConfig from either machine, It shows me their 192.x.x.x IP addresses and for the default gateway as well. from either computer I can do a successful 127.0.0.1 ping and both can ping the listed 192 address for the default gateway. 

Using the old computer (the one that WILL connect to the internet directly but not when the router is connected), I CAN ping the newer computer.  However, trying to ping the old computer from the new computer fails.  I can, however, access the files on the old computer from the new computer. 

Yesterday I swapped in a new NIC to the failing machine and everything remained exactly the same.  What is going on here !???  I desperately need my newer computer to have internet access. 

[MendMyComputer]

What you do know is
1) If networking between coputers attached to the router works fine (then Nic's shouldn't be your problem)
 forget the fact that your secondary PC doesn''t seem to be responding to Ping requests fro the main one (this is likely to be because of a firewall on the 2nd PC blocking/ignoring ping requests)
2) If your secondary machine connects to the internet fine direct in to the modem but your Main one doesn't due to not recieving an IP Address (Have you powered down the modem and retried?

Knowing that with your original setup i.e router, modem and both PC's all was fine except for the internet - are you able to log into the router to run diagnostics (what Make and Model is it??)
It may be that it's no longer set to pick up an IP address from your modem automatically using DHCP, making your internet not work.

It does worry me though that your Main PC won't connect directly via the modem - this should definately work if the modem has been rebooted as you state that it's fine on the internal network via your router

 

[Frank12345]

3) Did you try safe mode with networking? If not, please do.

I tried this.  It failed.