Internet connecting and disconnecting continuously?

[maheshhraut]

It happened suddenly. I'm not able to access Internet. Have a look at this gif, may be you will get better idea

I have no modem or router. Ethernet cable is directly plugged in my computer. Also there is no problem with my internet connection.

 

[Ralston18]

Your posting is a bit unclear. You state you are not able to access the internet and then say there "is no problem with my internet connection".

I think that you mean other devices on your network can reach the internet but not the device in your video (.gif) - correct?

You need to have a modem and router combination or a modem/router in one unit. Where does the ethernet cable plugged into your computer come from? If a wall outlet then you need to trace the wiring further back to some other device. That device make and model would be helpful.

The easiest thing to do first of all is to try replacing the ethernet cable between your computer and the other device. Use a cable that you know to be working.

Could also be just a loose connection somewhere. If the cable swap does not work and you have a ethernet wall outlet/port check inside that. Individual wires do come loose.

If you do not how to do that find a friend who can do so. Make sure it is not a power outer - an ethernet outlet. One that you can plug in an ethernet cable to. Nothing else.

 

[maheshhraut]

Device in gif is my PC running windows 7 ultimate.
It's only device that's not ablt to access Internet.
I bought new router. Plugged main Internet cable into my router. Connected router and PC with another cable. I can access Internet with my phone through WiFi. But my PC still not able to access Internet. I'm a noob when it comes to computers. Few of my friends told me that there could be problem with my LAN card. So i ping 127.0.0.1
Result is similar to what shown in image.

https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcRIXVxNZMjzDK9RplpX7p6fcDYEY-DArbeVXhLyWo2R4YIjVSHq

 

[Ralston18]

Ping 127.0.0.1 is basically a special test for testing your own computer. 127.0.0.1 is also referred to as "localhost".

Sort of helps but not as much as is necessary.

If your PC could not access the internet with the old router or the new router then, yes, it could be a LAN card problem.

However, that problem could also be the LAN card driver or some related network misconfiguration. The misconfiguration could be on the router or on the computer. Would you be able to reinstall the LAN card driver or find someone to help if necessary?

Suggest that you try this first:

Run "ipconfig /flushdns" at the command prompt (where you ran the "ping" command) and without the quotation marks.

If that does not resolve the problem (meaning still no internet access) then run "ipconfig /all" from the command prompt and post the results.

Would be helpful to know your router's make and model.

The purpose being to look for signs that something is misconfigured with respect to your computer.

 

[maheshhraut]

Thanks for your responses. There's an update, unlike the gif in my first post, now it is showing red X on my internet icon.
I'm sorry but I forgot to speak of important thing in my previous posts. I usually used to see yellow light blinking at ethernet port (i guess that's what it is called) when my internet was working. But since when my internet stopped working, I don't see any lights blinking where I connect the the cable whose other end is connected to router.
Regarding drivers, I updated my network drivers but it didnt help.
My router is TP-Link TL - WR740N (150 M).
THINGS I HAVE TRIED SO FAR-
1) Ran windows network troubleshooter, it says ethernet cable is unplugged
2)Tried command netsh winsock reset, didn't help.
3)I tried using my phone's internet on my pc by usb tethering and surprisingly it works. I can use my phone's internet on PC
4)I ran the commands you spoke of--


C:\Users\Mahesh_2>ipconfig /flushdns

Windows IP Configuration

Successfully flushed the DNS Resolver Cache.

C:\Users\Mahesh_2>ipconfig /all

Windows IP Configuration

Host Name . . . . . . . . . . . . : Explorer
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Mixed
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No

Ethernet adapter Local Area Connection:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek PCIe FE Family Controller
Physical Address. . . . . . . . . : 00-30-67-44-08-59
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes

Ethernet adapter Local Area Connection 8:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Remote NDIS based Internet Sharing Device

Physical Address. . . . . . . . . : 02-68-6D-77-17-00
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::90f:38ad:de11:e2fa%23(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.42.89(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Tuesday, November 10, 2015 01:01:56 AM
Lease Expires . . . . . . . . . . : Tuesday, November 10, 2015 02:01:55 AM
Default Gateway . . . . . . . . . : 192.168.42.129
DHCP Server . . . . . . . . . . . : 192.168.42.129
DHCPv6 IAID . . . . . . . . . . . : 503474285
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-1B-5B-6D-B0-00-30-67-44-08-59

DNS Servers . . . . . . . . . . . : 192.168.42.129
NetBIOS over Tcpip. . . . . . . . : Enabled

Tunnel adapter isatap.{2CDF00EC-14AA-43A3-ADB3-DAEB835A6258}:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Microsoft ISATAP Adapter
Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes

Tunnel adapter Reusable Microsoft 6To4 Adapter:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Microsoft 6to4 Adapter #2
Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes

Tunnel adapter 6TO4 Adapter:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Microsoft 6to4 Adapter
Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes

Tunnel adapter Teredo Tunneling Pseudo-Interface:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Teredo Tunneling Pseudo-Interface
Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes

Tunnel adapter isatap.{7DE19FCB-1B14-499A-9EC9-97E032AFA3E4}:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Microsoft ISATAP Adapter #2
Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes

C:\Users\Mahesh_2>

 

[maheshhraut]

While downloading realtek drivers from their website, I found something called as realtek Ethernet diagnostic utility.
I downloaded and ran the test. Here's a video -

https://drive.google.com/file/d/0Bxz_eo6PD4TsR19xUG40RmdleWs/view?usp=docslist_api

 

[Ralston18]

Did you note the results of the cable diagnostic?

Pair 1-2 "short": That means the two wires are touching somewhere.

Pair 3-6 "mismatch": That probably means that wire 3 and wire 6 are reversed on one end of the cable.

The yellow and red "X"s you see also indicate a bad cable or connector. Failing and then failed.

Also the response that "the cable is unplugged". A broken/cut wire has the same effect as being unplugged.

Most likely the router's LAN port you are using does not light up either. Look closely and make sure that you are looking at the correct LED/indicator light. The TP-Link manual I found shows that the light is either on ( device connected) or off (no device connected).

Try another ethernet cable from a computer that is correctly working on another network. Do not use any of your cables - especially if they were purchased as a batch or from the same source.

Make the connection directly from your computer's LAN card to a known working LAN port on your router.

 

[maheshhraut]

Problem is solved now. It was my lan card. I never thought it would be lan card as in device manager it was showing that my lan card is working properly. Anyway I replaced it and now I'm able to access internet

 

[Ralston18]

Makes sense. The card may be working properly (however device manager determines "properly") but the LAN card port where the cable is plugged in was damaged. I.e., the problems indicated by the cable diagnostic.

Easy to damage ports if the ethernet cable gets suddenly pulled for some reason or another. Or someone tries jamming the plug in upside down, etc., etc..