Wired network stopped working.

[davey]

I have 2 computers on a router connected to a cable modem. The setup's been working for years, but suddenly I can't get a connection. I remove the cable to Computer 1 and plug it directly to the modem. It works. So it must be the router's gone bad, right? So I buy a wireless router (since wired ones are no longer available, apparently), called Tenda brand. The computer thinks it's connected but can't get on the Net. I connect Computer 1 to the modem, it works. I connect Computer 2, in another room, directly to the modem. It can't connect.

I put Computer ! on the new router by itself. The lights are all doing what they're supposed to, but it can't connect.There's no manual with the new router except a useless "quick connect". I'll call tech support in the morning, but don't expect much.

To sum up: now there are 2 problems that don't have any logical connection I can think of:

1. The new router won't connect either computer to the Net through the cable. (Neither computer has a wireless card, as I prefer a wired connection)

2. Computer 2 won't connect even when its cable is plugged directly into the modem, even though this works with Computer 1.

Any thoughts before I toss the whole mess in the alley and go computer-free?

[muungwana]

I experienced the same thing a few years ago. Connecting one computer to the cable modern and it can go online, connecting second computer and it cant.

I couldnt find the reason but i suspect the modem remembers the last computer it connected to and only want to connect it. That could be the reason and could not, i dont know, i didnt test it enought to find out the problem.

Try connecting the router to the cable modem and then turn both off by unplugging them from electric outlet. Wait for around two minutes then turn on the modem first then turn on the router and then connect your computer to the router and then check to see if it will work

[davey]

muungwana, tried your routine, didn't work. The computer thought it was connected but can't open any Web pages or connect to email. Back to the direct modem>computer connection. Thanks for trying.

[muungwana]

How do you know the computer though it was connected? Maybe the problem is a router dns setting.

when connecting the computer to the router, run these two commands and report generated output for both of them

ping -c 1 google.com

ping -c 1 8.8.8.8

[GermanTux]

Davey;

Can you login to your router via the web interface, and see if it's WAN interface is pulling up an IP from your ISP? 

First, check your default gateway on PCLOS (do this when you are connected through your router):

-Open a terminal

-Type in "su" then hit enter. 

-Enter your root password.

-Type in "route -n" then press enter. 

The bottom entry in the gateway column is your default gateway.

-Open a web browser.

-Type in that default gateway address into it.  You will be prompted for a username and password.  Your router manual should have these available.  You will then need to find inside the menu that "status" tab/button/whatever, which should show your WAN IP settings. 

[davey]

muungwana, The Network icon said the network was up. Sometimes, even though it couldn't connect to websites. The result of the commands you suggested doesn't look very useful:

[dave@localhost ~]$ ping -c 1 google.com
ping: unknown host google.com
[dave@localhost ~]$ ping -c 1 8.8.8.8
connect: Network is unreachable

GermanTux, Here is the output:

[root@localhost dave]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 lo

When I put 0.0.0.0 into the browser I get Cannot connect. No prompt.

[smileeb]

I have 2 computers on a router connected to a cable modem. The setup's been working for years, but suddenly I can't get a connection. I remove the cable to Computer 1 and plug it directly to the modem. It works. So it must be the router's gone bad, right? So I buy a wireless router (since wired ones are no longer available, apparently), called Tenda brand. The computer thinks it's connected but can't get on the Net. I connect Computer 1 to the modem, it works. I connect Computer 2, in another room, directly to the modem. It can't connect.

I put Computer ! on the new router by itself. The lights are all doing what they're supposed to, but it can't connect.There's no manual with the new router except a useless "quick connect". I'll call tech support in the morning, but don't expect much.

To sum up: now there are 2 problems that don't have any logical connection I can think of:

1. The new router won't connect either computer to the Net through the cable. (Neither computer has a wireless card, as I prefer a wired connection)

2. Computer 2 won't connect even when its cable is plugged directly into the modem, even though this works with Computer 1.

Any thoughts before I toss the whole mess in the alley and go computer-free? 

Could the internet card in computer 2 be bad.

[btrussell]

muungwana, tried your routine, didn't work. The computer thought it was connected but can't open any Web pages or connect to email. Back to the direct modem>computer connection. Thanks for trying.

If the PC wasn't rebooted, it will be trying to still work via old address. May be new address after resetting modem and router.

[GermanTux]

GermanTux, Here is the output:

[root@localhost dave]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 lo

When I put 0.0.0.0 into the browser I get Cannot connect. No prompt.

OK, you have no valid IP address.  That is definitely problem #1 at the moment.  As recommended, have you tried rebooting your computer?  Try that (while plugged in to the router), and then type in the same "route -n" command again.  You currently have only a loopback connection, which just means that TCP/IP is working correctly. 

[horusfalcon]

Before reading anything I have to say, you may want to look at:

http://www.tenda.cn/tendacn/support/show.aspx?articleid=224

It seems what you describe is a common problem with Tenda's gear.  They discuss steps to a solution at the URL above.

This may be a silly question, but it's the "obvious" stuff that tends to bite me most often, so...

Is the cable/DSL modem connected to the Wide Area Network (WAN) port on the router?  If not, and one of the computers is plugged in there instead, it could cause the type of problem you are seeing (albeit with other odd effects, usually).

The interconnect should look like this:

MODEM ---------- WAN
Computer 1------ LAN Port (any)
Computer 2------ LAN Port (any other)

Me, I would put computer 1 in port 1 and computer 2 in port 2 just for ease of identification, but any of the four or five LAN ports on a typical home-use router should work.  Just make sure the WAN port is connected to the modem and not a computer.

Here ends the "obvious" stuff.  Some other suggestions follow to help isolate the problem.

Try setting up static IP on the LAN side.  If both computers connect this way, something in your DHCP setup was off somewhere.  (Most modern routers provide a DHCP server which usually doesn't require too much setup. What do your docs say about it?)

Does either of the computers you have run Windows Vista as a dual-boot?  (This can make for unpleasantness in networking - Vista doesn't play well with others...)?  If so, the static IP setup will tend to work better for you.  Don't forget to make any Windows installation on the LAN static IP, too, if you decide this is the way to go.

Do you have the model number on your router handy?  It might help in digging into the problem in more depth.

You should be able to eliminate the problem with computer 2 (possible bad network adapter) by swapping/replacing the card (unless it's a laptop, in which case, look at a PCMCIA or USB/Ethernet adapter.  D-Link makes a nice USB unit for about $15 US).

Jot back with some more info and let's see if we can't solve this.  Networking problems tend to appear to be complicated until one finds the solution, usually with a "Doh!" and a head smack.  Just keep pluggin' at it, man... you'll get there.

Later On,
D

[davey]

Thanks, everybody, for all the ideas. Some changes since the original post:

1 -- Looks like the inability for computer 2 to connect directly was because I didn't properly power cycle the cable modem -- unplug the power and coax cables and wait a minute or so fro the modem to forget what it was doing before. Now I get a connection on each computer with the direct connection.

2-- After seeing the heads-up on the Tenda router above, and calling the so-called tech support line and getting the worst attempt to communicate I've ever experienced (and it's a very low bar), I ran out of patience and returned the thing. While I was looking for an alternative, a guy at Radio Shack thought that an ethernet switch might be all I need, since all I want to do is distribute the Net feed to 2 computers, but don't need to network the computers themselves together. It seemed logical: if I can connect one at a time, why wouldn't a switch tha works basically like a splitter do the trick. And I hate paying for a wireless router when all I want to do is make a connection with a cable that's already in place -- but nobody sells the wired kind anymore.  Well, the switcher didn't work,  and will be going back to the store. I still don't understand why it can't be used this way, but have to admit there's nothing on the packaging or manual that suggests it can. Maybe it has to do with the need to power cycle the modem, and the router somehow takes care of that?

Anyway, I'll be shopping for another router today or tomorrow and see what happens. Hope you'll stay tuned for the next installment.

[GermanTux]

Thanks, everybody, for all the ideas. Some changes since the original post:

1 -- Looks like the inability for computer 2 to connect directly was because I didn't properly power cycle the cable modem -- unplug the power and coax cables and wait a minute or so fro the modem to forget what it was doing before. Now I get a connection on each computer with the direct connection.

2-- After seeing the heads-up on the Tenda router above, and calling the so-called tech support line and getting the worst attempt to communicate I've ever experienced (and it's a very low bar), I ran out of patience and returned the thing. While I was looking for an alternative, a guy at Radio Shack thought that an ethernet switch might be all I need, since all I want to do is distribute the Net feed to 2 computers, but don't need to network the computers themselves together. It seemed logical: if I can connect one at a time, why wouldn't a switch tha works basically like a splitter do the trick. And I hate paying for a wireless router when all I want to do is make a connection with a cable that's already in place -- but nobody sells the wired kind anymore.  Well, the switcher didn't work,  and will be going back to the store. I still don't understand why it can't be used this way, but have to admit there's nothing on the packaging or manual that suggests it can. Maybe it has to do with the need to power cycle the modem, and the router somehow takes care of that?

Anyway, I'll be shopping for another router today or tomorrow and see what happens. Hope you'll stay tuned for the next installment.

Ahhhhh!  Never listen to the people at radio shack....  The problem with a switch is that your ISP would need to give you two public IP addresses (assuming two computers were connected).  This is possible, but your ISP would almost certainly charge extra.  Sorry to hear the Tenda router did not work. 

Buy this router.  You can shut off the wireless interface if you do not want to use it.  These things are great, and almost indestructible.  Their default firmware - though basic - is great for stability and uptime.  The routers you get in the store these days are almost universally crap. 

[davey]

I went and bought another router before seeing your suggestion, GermanTux. Picked up a Belkin G for 25 bucks, and all seems to be working again. So the confusion came in when the new Tenda router turned out not to work. Thanks for all the help.

Only 2 issues remain:

1 -- page loads seem slower than they were before. Any settings that might need looking at for the new router/config?

2 -- since I'm not using the wifi part, how do I turn it off and only use the cabled route?

[horusfalcon]

I went and bought another router before seeing your suggestion, GermanTux. Picked up a Belkin G for 25 bucks, and all seems to be working again. So the confusion came in when the new Tenda router turned out not to work. Thanks for all the help.

Only 2 issues remain:

1 -- page loads seem slower than they were before. Any settings that might need looking at for the new router/config?

2 -- since I'm not using the wifi part, how do I turn it off and only use the cabled route?

I have to second comments about Radio Shack - their sales force is generally too motivated to make a sale to point the customer at what they really need.  Once in a while you find someone there who knows the deal, but most of the folks who work there just seize on the first thing you say to them and know of some vaguely related gadget they think will fill your needs.

Get rid of the Belkin if you want something dependable.  A lot of folks may disagree with me on this, but I've not seen anything by Belkin more sophisticated than a cable or cable adapter that was worth beans.  LinkSys isn't bad gear since Cisco bought them out, is generally widely available, and I've always been a fan of D-Link's gear.  Netgear is pretty good, too, but is sometimes more interesting to get set up correctly.

Look at D-Link's site; I think they even still make a non-wireless model... hang on.

Yup,  here it is:  http://www.dlink.com/products/?pid=478

Back to your questions:

Most routers these days have a web interface that can be accessed by pointing your browser at http://192.168.1.1 or http://192.168.0.1 so consult the documentation with your router and see where that is.  The very first thing you should do after your network is working is change the default password for the router's administrative account to something only you know and can remember.  This may save you from being pwned by some bored script kiddie trying to expand a botnet.  If you're really paranoid (and I'm not, myself) you can also change the address of the router to something less obvious, but it's not really necessary as long as you use a strong password and don't share it with anyone.  (It might also mean having to change the setup in your modem, too...)

After you've secured your router with a new password, look around in the web interface menu at the options you have.  Different router manufacturers have varying ideas about how to organize and set up their equipment, so it's best to get familiar with the interface before making too many changes.  Without knowing your specific router's model number, the best I can do for now is point you at:

http://en-us-support.belkin.com/app/product/list/q/routers/

I kinda bumble through networking, myself.  I have to break out the books a lot when it gets interesting. This site is a decent intro to how routers work in general.

Here's one thing I do know:   if you use BitTorrent for anything, look at limiting your upload speeds and max number of connections in your client (example BT clients are Ktorrent, Transmission, and Azureus - there are lots more, too).  Otherwise, the sheer massive number of connections BT uses will swamp your router's routing tables and slow things down.  Sounds like this may not be an issue for you, though.

I hope you get things moving the way you want.  I gotta get ready for work just now, but maybe someone else out there will have some ideas?

Later On,
D