It is very frustrating when you are unable to access the Internet on your computer but the ISP technical support repeats everything is fine at their side. There are so many reasons which can prevent connectivity on your local network like DNS issues, faulty Ethernet cable or modem etc. This article explains basic troubleshooting steps you can follow to test your local network when you face Internet connectivity or file sharing issues. To test a local network, we do not need high networking knowledge. If you read this tutorial carefully, you will find it very simple.
These four steps are the very basics to test a local network. This tutorial just gives guidelines only because here I showed one of the simplest network to troubleshoot. As the number of devices connected to the network increases, it will be difficult to test the network.
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- Find Network Topology
At first, you must understand how devices are connected to the LAN before starting the troubleshooting. In this example, I assume the PC is connected to the router using an Ethernet cable. The router is connected to the modem. So the network topology is as below.
Modem----Router---PC - Ping Router
We need to ping the first device connected to your PC. Here in this example, it is the router. So you must type the following command on Command Prompt and press enter.
ping [router IP]
If you do not know the router IP address, type the following command on Command Prompt and press enter.
ipconfig
Now you will get the Default Gateway address. It is the router IP address(I assume it is 192.168.1.1). So to check the connection between the router and your computer execute the following commands.
ping 192.168.1.1
We need to ping the router even if you are getting default gateway because this value may be shown on DOS from the cache. If you are getting a reply then we can proceed to step2. - Ping the Modem IP
If you do not know the modem IP address, I suggest you follow the instructions provided in the link below.
How to Find Log on IP Of a Device
Here I assume the respective IP address is 192.168.0.1 and to ping modem, use the following command.
ping 192.168.0.1
If you are getting replies from the destination, the connection between your computer and modem is perfect. The issue must be at ISP side. - No Reply From Modem
What if you are not getting valid replies from the modem. In this case, you must change the way of troubleshooting. While your computer is receiving replies from the router and not from the modem, we can pinpoint the issue as follows.- Your modem has no connection to the router.
- Modem is faulty
To fix the issue follow the steps below.- Check the Connection
Check the connection between modem and router. Make sure the LAN lights for respective ports are on. If you are not sure, unplug the cable and reconnect it. - Power cycle
We need to power cycle the entire network or at least modem. Disconnect power from the device and wait for one minute to reconnect power. To learn more about this step, I suggest you to read the instructions provided in the link below.
What is Power Cycle and How to Do It
- Your modem has no connection to the router.
- No replies from global DNS and Loop Back address
- Cannot go online and No replies from global DNS but getting a reply from Loopback Address
- Getting Replies From Global DNS Server
These four steps are the very basics to test a local network. This tutorial just gives guidelines only because here I showed one of the simplest network to troubleshoot. As the number of devices connected to the network increases, it will be difficult to test the network.
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