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. 

[Frank12345]

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

Alan <>< 

On the non-connecting computer, when I run IPCOnfig/all, it shows a 169 IP address and nothing for the default gateway. 

[Frank12345]

Yes.  You basically summed up my frustration here.  As far as I can tell, I have 2 functioning computers, functioning cables, a functioning cable modem, functional NICs, and a router that is functional for my local home network.  I have been through the settings a dozen times, and they are fine.  Yet I have TWO different problems, neither of which I can resolve.

My secondary computer connects to the internet when directly connected, but then if I

1)  simply pull the ethernet cord from the back of that computer and put it into my main computer, the main computer will not connect to the internet.   

 OR

2)  If I leave the main computer completely off and hooked up to nothing, but I simply try to connect the router as an intermediate device between my secondary computer and the cable modem, the secondary computer suddenly will not connect to the internet!   

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]

Bear with me here as I try to make some sense of this. 

When I have both computers hooked up to the router and the router to the cable modem, both computers are receiving 192.168 addresses and my home network is fully functional.  Neither computer connects to the internet. 

When I hook the main computer up to the cable modem directly, it receives a 169 IP. 

When I hook my secondary computer up to the cable modem, it works. 

What about this as a theory:  Something is wrong with the cable modem that prevents my main computer AND the router from communicating with it; however, for some unknown reason, my older secondary computer is unaffected by this problem. 

[MendMyComputer]

Getting back to seeing what the router can tell us about the link from it to the modem.

When you have your PC's hooked up to the router and you run ipconfig from a dos prompt what is your gateway address? (This will be the routers ip address for your home network)

You should be able to enter this into your web browser to get up the routers configuration page. Almost all brands of router will have a diagnostics section and detailed information for the WAN connection (i.e the link from it to the modem)

Can you try logging into your router for us and letting us know what you find?

[Frank12345]

It's a linksys Router 192.168.1.1

But, I am not sure what I am supposed to do next.  I typed this into my browser bar but all that di was perform a google search for that address, which returned a bunch of hits telling me this address is for LinkSys routers, which I already knew.  One of the links brought me to the LinkSys page, and I found a page that seems to giev steps to troubleshoot a problem, but whne trying to follow the steps, I ran into a problem trying to access the routers setup page:

<<<After connecting the router, open a Web Browser (Such as Internet Explorer or Netscape)
When the browser opens, go to the "Address" bar and input the Routers IP Address (The Routers default IP Address is 192.168.1.1) then click on the Go button or hit the [Enter] key.
A window will pop up prompting for a "User Name" and "Password", leave the "User Name" blank and input the Routers password (admin is the routers default Password) then click on the OK button.
After inputting the Password, the "Setup" page should appear. >>>


This did not happen.  All it does is bring up that same google search. 

[BC_Programmer]

you have to enter

Code: [Select]

http://192.168.1.1


[Frank12345]

Careless error on my part.  I was able to get into the setup page. 

On the "stauts" tab it is showing the IP address and subnet mask for the LAN. For the WAN, everything is showing zeroes. 

[Frank12345]

Can you try logging into your router for us and letting us know what you find?

What specifically am I looking for?

[midsail]

If u have a Firewall turn it off for testing purposes. See if u can connect to the internet without going thru the router. Connect to the modem directly. Do this on both computers. If u can connect to internet this way, we have narrowed the problem to 2 areas, Firewall or router.
1-If u have connected to the internet on each PC just turn on the Firewall one at a time on each PC.
2- go to the router manufacture and follow direction to reset router to factory defaults.
 I am inclined to start pionting a finger to the router. BTW can u barrow a router from a friend and connect to your network?

[Frank12345]

I have had firewalls turned off the entire time.  Also, I have been connecting the computers directly to the cable modem; that is the only way I can get online.  The secondary computer works when connected directly to the cable modem.

But the main computer will NOT connect (router not involved at all), AND, the secondary computer stops connecting if I try to use the router (main computer not involved at all). 

So I have two different failures there, each one involving isolation of equipment.  The only constant is the Cable modem.  I suspect that is the problem.  I cannot explain why the secondary computer (which I am on now) can connect.  But the issue is not the router.  My home network is working fine, and also, I swapped out the router for a new one, and all problems remained the same.

If u have a Firewall turn it off for testing purposes. See if u can connect to the internet without going thru the router. Connect to the modem directly. Do this on both computers. If u can connect to internet this way, we have narrowed the problem to 2 areas, Firewall or router.
1-If u have connected to the internet on each PC just turn on the Firewall one at a time on each PC.
2- go to the router manufacture and follow direction to reset router to factory defaults.
 I am inclined to start pionting a finger to the router. BTW can u barrow a router from a friend and connect to your network?

[Geek-9pm]

You need to be more specific.
You have a com cast cable internet service?
Which modem?
Why did you not rent the wireless router from them?
Which router do you have?
When you did get it to work. did you log all the information for reference?
You need to do a ipconfig /all and copy all the addresses.

I have Com cast cable modem here and have it  into a Net gear router.
It tool about 6 hours of research to find the answer. The answer  is in the documentai0on of the router and on many forums on the internet. YYou just google the name of your router and  comcast and find lots of people who had this problem.
The answer is the is almost always you have to ask the router do do a MAC clone.

Com cast blocks a port used for DHCP.  So you set the router to a MAC the modem knows. Then tghe router will do DHCP for the other PCs on the network.
It is late and I don't have time to edit this. 

Anyway, I now have about four PCs on the connection Using a older Net gear router. I set it to clone the MAC of the PC that works.

[Frank12345]

Comcast service, Motorolla SB5120.  I did not do wireless because I have no need for it.  The Router is a LinkSys Router.  I have written down all the working IP address info from when the computer is hooked up directly to the cable modem.  I went on the linksys website troubleshooting section and read the part where it says to do the MAC clone.  However, I could not find ANYTHING in the router's setup page that gave me an option to actually do this.  It certainly wasn't where the troubleshooting page said it would be. 

But the most imporetant thing is this: 

I do not care about the router right now.  I appreciate everyone's help with the networking issues, but right now my primary concern is that my MAIN computer will NOT connect to the internet even when connected directly to the cable modem. 

I fail to see how a router issue could be causing this, since the router is not involved in that equation.  All I need right now is to get my main computer hooked up to the internet.  I can deal with getting my home network reconfigured later. 

You need to be more specific.
You have a com cast cable internet service?
Which modem?
Why did you not rent the wireless router from them?
Which router do you have?
When you did get it to work. did you log all the information for reference?
You need to do a ipconfig /all and copy all the addresses.

I have Com cast cable modem here and have it  into a Net gear router.
It tool about 6 hours of research to find the answer. The answer  is in the documentai0on of the router and on many forums on the internet. YYou just google the name of your router and  comcast and find lots of people who had this problem.
The answer is the is almost always you have to ask the router do do a MAC clone.

Com cast blocks a port used for DHCP.  So you set the router to a MAC the modem knows. Then tghe router will do DHCP for the other PCs on the network.
It is late and I don't have time to edit this. 

Anyway, I now have about four PCs on the connection Using a older Net gear router. I set it to clone the MAC of the PC that works.

[Geek-9pm]

The modem wants the MAC of the PC that it made friends with. Otherwise you have to turn off the modem, turn off the computer. Turn both back on and let them get intimate. The modem wannest the MAC.
If that is the same modem I have. Which modem is it?

aaaaa... goodf nited. i am failiing asleeppp.

[Frank12345]

The modem wants the MAC of the PC that it made friends with. Otherwise you have to turn off the modem, turn off the computer. Turn both back on and let them get intimate. The modem wannest the MAC.
If that is the same modem I have. Which modem is it?

aaaaa... goodf nited. i am failiing asleeppp.

It's a motorolla SB5120.  And unfortunately, this problem is long past the point of restarting things and power cycling things.  I've been at this for  two weeks off and on; it's going to take more sophisticated measures.   I can try a MAC clone but I am having a hard time doing it?

[Geek-9pm]

Docs for Motorola SB5120.
http://support.cox.com/sdccommon/asp/contentredirect.asp?sprt_cid=be19f914-eb7a-4c96-a480-c4082dfb1791

Linksys Router Docs? We need the model number so we can search the docs and find out out how to change the MAC of the router so that it is the same as whatever PC gets into the modem.

As stated earlier, the modem does not care a bit about l your local IP address. It wants a MAC. It fell in love with your old computer and will not talk to anybody else. So you have to give the router that MAC
It has to have the MAC. Everything else is automatic once the modem sees the right MAC.

Once the router has the MAC, it knows what to do. It will hide the old PC from the modem and pretend to be the old PC. The modem will gush lots of TCP//IP and the router will do DHCP and you can have many PCs on the router.

Reset the old PC and the router will give it a local IP.

Sorry about my poor writing skills.

[Frank12345]

I want to make sure I understand what you are suggesting here.  Are you saying that my cable modem has "locked on" to the MAC of my secondary computer, such that it is not recognizing either my main computer or my router?   If that is the case, I don't understand what you are suggesting as a fix.  I do not know how to open the settings page for the cable modem to tell it to recognize my other hardware.   I checked that page you linked me to for troubleshooting the modem, but that page has no useful information. 

Docs for Motorola SB5120.
http://support.cox.com/sdccommon/asp/contentredirect.asp?sprt_cid=be19f914-eb7a-4c96-a480-c4082dfb1791

Linksys Router Docs? We need the model number so we can search the docs and find out out how to change the MAC of the router so that it is the same as whatever PC gets into the modem.

As stated earlier, the modem does not care a bit about l your local IP address. It wants a MAC. It fell in love with your old computer and will not talk to anybody else. So you have to give the router that MAC
It has to have the MAC. Everything else is automatic once the modem sees the right MAC.

Once the router has the MAC, it knows what to do. It will hide the old PC from the modem and pretend to be the old PC. The modem will gush lots of TCP//IP and the router will do DHCP and you can have many PCs on the router.

Reset the old PC and the router will give it a local IP.

Sorry about my poor writing skills.

[Geek-9pm]

You have the general idea of how it works. However, getting the modem to recognize a different Mac address will not resolve the issue. The modem only wants to communicate with a single address. It does not do DHCP assignments. The router must do DHCP  IP assignments. The router must have the MAC address recognized by the modem. All traffic will be directed to the router, and the router will do its job to send stuff to the individual computers based on the IP addresses it assigned to the local computers.
So either you have to dig into them router documentation and find out how to assign MAC or else try another router.
As far as I know all lLinkSys routers have this ability. What is the model number of your router?

[Frank12345]

The Router is  a LinkSys NR041. 

But a few days ago I bought another router and hooked it up; the problem remained. 

You have the general idea of how it works. However, getting the modem to recognize a different Mac address will not resolve the issue. The modem only wants to communicate with a single address. It does not do DHCP assignments. The router must do DHCP  IP assignments. The router must have the MAC address recognized by the modem. All traffic will be directed to the router, and the router will do its job to send stuff to the individual computers based on the IP addresses it assigned to the local computers.
So either you have to dig into them router documentation and find out how to assign MAC or else try another router.
As far as I know all lLinkSys routers have this ability. What is the model number of your router?

[Geek-9pm]

Yes, your router does have an option to change the MAC address.
There was a firmware revision that made this a separate tab. But even if you have the earlier firmware it's still in there somewhere.

Here in this forum we are volunteers and do not get paid for this work. I personally do a lot of research on this and found that on many forums the common thought is that you have to use a MAC address. It is possible to get a connection without using a that feature, but you will not be able to share the connection with other computers and the connection is not reliable.

I'm going to give you a link to another forum where this has been directly answered in very clear terms. Both Comcast and Linksys but agree that you're supposed to clone the address of the primary computer. In this context primary computer means the one that Comcast used to set up your system.
Apparently there is some feature where the modem will pick up a new MAC address, but the documentation is not clear on how it does this. So the generally rule is you use the address that is working and go from there.
It appears that Comcast locks on to the first computer at fines during the installation process. There is some way to reset the modem, but that doesn't resolve the problem. You still have to change the MAC used by the router.
Muse over the link below and notice somebody  put  this question quite directly and the answer they get is simply you have to clone the MAC.

http://www.dslreports.com/forum/remark,15536499

For more information just Google: LinkSys Comcast MAC clone

[Frank12345]

I appreciate all the help.  I finally did today what I should have done weeks ago - I took the modem back to comcast and got another one.   And now my main computer is working.  I am thrilled.  But, I am worried that if I try to set up my network again, the same problem will occur.  I still don't understand how it happened in the first place.  I had used both computers for over a year without incident, and it was the secondary computer that was working and not the primary one that comcast set up.  And of course this problem happened out of nowhere without anyone making any changes or doing anything. 

Yes, your router does have an option to change the MAC address.
There was a firmware revision that made this a separate tab. But even if you have the earlier firmware it's still in there somewhere.

Here in this forum we are volunteers and do not get paid for this work. I personally do a lot of research on this and found that on many forums the common thought is that you have to use a MAC address. It is possible to get a connection without using a that feature, but you will not be able to share the connection with other computers and the connection is not reliable.

I'm going to give you a link to another forum where this has been directly answered in very clear terms. Both Comcast and Linksys but agree that you're supposed to clone the address of the primary computer. In this context primary computer means the one that Comcast used to set up your system.
Apparently there is some feature where the modem will pick up a new MAC address, but the documentation is not clear on how it does this. So the generally rule is you use the address that is working and go from there.
It appears that Comcast locks on to the first computer at fines during the installation process. There is some way to reset the modem, but that doesn't resolve the problem. You still have to change the MAC used by the router.
Muse over the link below and notice somebody  put  this question quite directly and the answer they get is simply you have to clone the MAC.

http://www.dslreports.com/forum/remark,15536499

For more information just Google: LinkSys Comcast MAC clone

[Frank12345]

After getting my main computer back online, I decided to try to set up my home network again, using the new cable modem but the same router as before. 

It failed.  With the router set up, neither computer would connect to the internet.  Much to my relief, upon disconnecting the router and connecting my main computer directly, it still worked. 

Does anyone have any ideas on what is going on with the router?  It works for my local network but won't allow either computer to connect to the internet.  I am still puzzled about this. 

[Geek-9pm]

The modem prefers a MAC address. Without a MC address, the connection will reset from time to time. With ta proper MAC address the connection reset will be transparent to the user.
The modem does dynamic Internet IP assignment. This is a feature of cable modem operation.
It will connect with one computer. Only one.
Just one time you must  give the MAC of the PC that was last on-line to the router. From then on the router will revive the Dynamic assignment from the modem,  whenever the modem wants to play tag.
The router, in turn, will assign local IP address for  all your computers.
Please rared your documentation.