Question Ethernet cable gets detected by a single computer but not others

[Miguel Montoya]

Everything was working all right just before I went internetless because of my ISP for about a year. Basically, my configuration is set as follows: 2 computers (a PC and a laptop) always connected to a 8-port switch, which is connected to an ADSL modem (through the LAN port on it). I meant all right because I was able to get internet to both computers through the switch connected to the ADSL modem by the ethernet cable.

ISP -> ADSL modem -> Switch -> 2 computers

The problem began once my internet connection was reinstated, which happened like 4-5 months ago. Now my laptop is the only one who detects the ethernet cable (and gets connected to internet) when it is plugged in directly into the ADSL modem since the switch no longer recognises it. The switch, like every other switch out there, lights up a LED to indicate that a certain device is attached and successfully connected to it; mine works normally when you attach any computer into it (I'm even able to set up a local network by attaching multiple computers to the switch to transfer file amongst computers); however, once you plug in the ethernet cable from the ADSL modem, it doesn't work, the LED where the ethernet cable is plugged in keeps blinking like every 20 seconds and after a few minutes it just lights off, so I'm not getting internet to the rest of the computers attached to the switch any more. Even attaching another computer directly into the modem (except the laptop, as I said earlier) won't work either. The ethernet cable doesn't get detected by the operating system (I've tried both Windows and Linux-based OSs, and it just the same).

I simply don't have any clue as to what could be happening here, may it be the ADSL modem, which is kind of old since I've been using for 5-7 years straight without any firmware update? I've reset the ADSL modem many times from both the web interface and the physical small button next to the ADSL port.

Do you have any ideas what is going on here?

 

[Lutfij]

Are both system's running the same OS? If Windows 10, which version are you on? If prior to Windows 10, are you on the latest BIOS update for your motherboard and the latest drivers for your networking adapter? You could try uninstalling and reinstalling the drivers.

 

[Miguel Montoya]

Are both system's running the same OS? If Windows 10, which version are you on? If prior to Windows 10, are you on the latest BIOS update for your motherboard and the latest drivers for your networking adapter? You could try uninstalling and reinstalling the drivers.

Both computers are running on Windows 10; however, I've already tried reinstalling both the OS (Windows 10 or other Linux-based) and the drivers (when I'm on Windows 10) uncountable times going nowhere since the problem persists. What seems strange to me is the fact that is was working before I went internetless, it was giving no problems at all (the internet just work all right across all the computers using the switch), but now the ethernet only gets detected by the laptop. Honestly, I have no clue as to why.

 

[SgtScream]

If the link light goes out completely, that some sort of hardware issue. Is the device owned by you or the ISP?

 

[Miguel Montoya]

It's owned by me.

If the link light goes out completely, that some sort of hardware issue. Is the device owned by you or the ISP?

It's owned by me. At first I thought it could've been some sort of system corruption on the modem since there was multiple times throughout the year without internet (nowadays it happens sometimes too) when the modem was attached to power source and a blackout would reach us, but if that were true, it wouldn't work on the laptop, would it?

 

[SgtScream]

I'd try factory re-setting it then ultimately replacing it for testing. Just keep in mind if you factory reset, you may have to reconfigure everything.

 

[Miguel Montoya]

I think I can discard any problem on the switch because I'm able to set up a sort of local network amongst computers (I've got to give each one of them a static IP to achieve communication, though).

 

[SgtScream]

So DHCP doesn't work is what you're saying. Can you share your ipconfig /all output on both computers with DHCP enabled on both devices? Enable dhcp, restart both devices, enter that command and post the output on this thread.

 

[Miguel Montoya]

I'd try factory re-setting it then ultimately replacing it for testing. Just keep in mind if you factory reset, you may have to reconfigure everything.

As I said, I've already tried that uncountable times from both the web interface of the modem and by pressing the physical small button meant for reset.

 

[Miguel Montoya]

So DHCP doesn't work is what you're saying. Can you share your ipconfig /all output on both computers with DHCP enabled on both devices? Enable dhcp, restart both devices, enter that command and post the output on this thread.

No, no. The switch is an unmanaged switch, so I have to do that when I'm setting up a local-like network amongst my computers. The problem is on modem, it was working all right (it was giving unique IP addresses to each computer attached to the switch, since there was a working connection between the switch and modem) before I was without internet.

Now if I try to plug one end of the ethernet cable into a port on the switch and the other end into the LAN port on the modem, the LED supposedly to be light on it's not (at least after a few minutes of blinking) , hence it won't give any internet to the rest of computers attached to the modem. Look:

ISP -> ADSL modem -LAN port> Laptop = This will work. I get full internet connection.
ISP -> ADSL modem -LAN port> Switch -> Laptop = Won't work. The modem doesn't get recognised by the switch
ISP -> ADSL modem -LAN port> Other computer = Won't work. The computer doesn't detect the ethernet cable.
Switch -> Computers attached to it = Will work. I'm capable of setting this kind of network with no problems at all. This way I'm looking if the problem resides on the switch, which is not, since it works perfectly.

 

[SgtScream]

What ip address does the switch have?

 

[Miguel Montoya]

What ip address does the switch have?

It doesn't have any. It only serves as a bridge between the internet connection given by the modem and the rest of the computers attached to it. The ADSL modem would give a public IP address for every computer attached to the switch, it is not a router, so it doesn't set a private network.

 

[SgtScream]

If it's a switch, it has an internal ip address. You should be able to web interface to it via the ip. Try changing the internal ip for that device to rule out an ip conflict.

 

[Miguel Montoya]

I have to change the IP address, subnet mask and default gateway to be able to access the modem's web interface, hence I won't be able to reach internet unless I go back to default configuration, so I get a public IP address again. I think I don't need to do that change if I'm dealing with a router, do I?

 

[Miguel Montoya]

If it's a switch, it has an internal ip address. You should be able to web interface to it via the ip. Try changing the internal ip for that device to rule out an ip conflict.

It's an unmanaged switch, as I found on the manufacturer's website, meaning I don't have nor can I access to any interface given by the switch.

 

[SgtScream]

What is the make and model of the adsl modem?

 

[Miguel Montoya]

What is the make and model of the adsl modem?

It's a Huawei modem and it says:
Product: ADSL CPL
Model: SmartAX MT882a

 

[SgtScream]

Can you message me screen shots of your router settings? I don't want you to post any external ip information.