two router with same IP was connected to the same LAN

[alliv143]

Hello everyone!

I hope someone can help me. I have this nightmare of a problem in our LAN.

It all started when I tried this new wireless router (TP-LINK TL-WR541G/TL-WR542G) and connected it on our LAN. I wasn't able to change the default IP which is 192.168.1.1, the same IP as our current linksys (EtherFast Cable/DSL router). Later though, I also was able to change the IP of the wireless router to 192.168.2.1.

I started getting help calls about (winxp) computers in our LAN that can't connect to the internet. I have to do a 'REPAIR' so that they can connect to the internet. Then in a while, it reverts to looking for the wireless router yet again, thus cutting the internet connection. I tried to connect to the router on a non-connecting computer by entering 192.168.1.1 in the address bar, and to my surprise, it was looking for the wireless router! Not the linksys cable/dsl router! When I do a repair, and try this again.. it then finds the correct linksys cable router.

Question is, how do I clear this wireless router from the computers? How do I prevent the computers from looking for this wireless router. Why do they revert to it? But when I do a repair, it goes back to the linksys cable router. I already disconnected the wireless router and powered it off, yet, the winxp computers seem to cycle-locate between the two routers.

Any help will be greatly appreciated!

Thanks!

[alliv143]

Hmm.. I think I should make this a bit clearer:

- The two routers were connected to the modem (w/ 5 public IP's available) but, using different public IP's provided by the ISP.

- The two routers have the same IP which is 192.168.1.1.

- I've already disconnected the wireless router, so what's left is the router cable.

- Ever since then, winxp computers connected in the LAN would sometimes connect to the internet, but, they suddenly get disconnected because it suddenly connects to the other router (which was already disconnected). Why it happens, now that I don't understand. I have to do a 'repair' in order to re-establish to the cable router.

How can I solve this problem?

Please help.

Thanks!

[johnwill]

That's about the most confusing two posts I've seen!

I have no idea what is connected to what, I think you need to start debugging this logically!


I'm assuming you have the broadband modem, then a switch to split the modem output to the two WAN ports of the routers, correct?


Are both routers wireless routers? What capability are you using here?


Can you draw a diagram of how all of this is wired up?

[alliv143]

Originally Posted by johnwill

That's about the most confusing two posts I've seen!

I have no idea what is connected to what, I think you need to start debugging this logically!


I'm assuming you have the broadband modem, then a switch to split the modem output to the two WAN ports of the routers, correct?


Are both routers wireless routers? What capability are you using here?


Can you draw a diagram of how all of this is wired up?

Hi John! Actually, I am confused as you are!

You are correct about how the two routers were connected to the broadband modem:

Broadband modem
______|
Switch/Hub (5 public IP's provided by ISP)
______|_____________
___| _______________|
Cable router _____Wireless Router
___| _______________|
Main LAN ______Wireless Equipments

One router is wireless (TP-Link) and the other a cable router (Linksys). The cable router connects to our main LAN using one of the public IP's provided by our ISP. The wireless router also uses another public IP different from the cable router. This is used only for wireless equipments and is not connected in the main LAN (cabled).

The puzzling thing about this is that, when I try to access the cable router setup via the browser (192.168.1.1) of an affected computer (means there is no internet connection and the unit is of course connected on the Main LAN), I get the wireless router (TP-Link) instead! And when I do a network 'repair', it suddenly switches back to the cable router, I can access the router setup (Linksys) via 192.168.1.1 in my browser, and I have an internet connection again!

I disconnected the wireless router from the setup, and rebooted everything, modem, switch/hub, routers, etc. I also rebooted the affected computer and did a 'repair' again to flush out the network settings that might still linger. Still this happens, the LAN-connected computer just suddenly switches, or try's to connect to the wireless router, even though there is no way that should happen. The OS of the affected computer is winXP and they dont have wireless connection capability. This problem doesn't happen with win vista computers.

I don't really have a clue on what's going on.. is this a virus on the affected computer? Or am I missing something here?

Please help. Thanks!

[johnwill]

First off, I'd recommend a couple of things.

Change the base address of one of the routers so they are not in the same subnet. Say, 192.168.2.1 for one of them.

Next, I'd like to see the following from one of the computers on the wired LAN and one on the wireless LAN.


Hold the Windows key and press R, then type CMD to open a command prompt:

In the command prompt window that opens, type type the following command:

Note that there is a space before the /ALL, but there is NOT a space after the / in the following command.

IPCONFIG /ALL

Right click in the command window and choose Select All, then hit Enter to copy the contents to the clipboard.
Paste the results in a message here.

If you are on a machine with no network connection, use a floppy, USB disk, or a CD-RW disk to transfer a text file with the information to allow pasting it here.

[alliv143]

Hello John, everything's ok now. I finally discovered the culprit behind my miseries! Someone in our network connected a router into the LAN (same model). I discovered the difference between the two via the mac address displayed in the setup. They tried to use the router as a dumb switch, unfortunately, they didn't even consider reconfiguring its setup first. Once I configured it's IP and disabled DHCP, everything went back to normal.

Thanks again for your help!

[johnwill]

The usual suspect, dumb users!