Solving a network problem can be hard and frustrating. While you can check your internet connection using the Windows Network Diagnostic tool, it is hardly enough to solve most problems. Sometime, you might have to troubleshoot via the hard way – the command line way.
There are several advantages to using th command line instead of the visual interface:
- We can check on individual item, and isolate those that are causing the problems.
- Command line tend to have more options so we can test the system deeply.
- We can use scripts to automate the process.
In this article, we will show you how to diagnose and fix network problems using the command line.
To get started, first make sure that you are running the command prompt with Administrator privilege.
How to know if your cable is connected
You can use the
ipconfig tool to check if you are experiencing some problem with your cable. Windows will show up a list of the interfaces and if they are connected or not.
How to know if your gateway is working
A gateway is the device, usually a router, that connects your computer to other networks and Internet. If you cannot connect with your device, it is pretty sure you are not going to connect to the Internet. First you need to know the IP address of the device. You can use
Ipconfig to give us the information about the default gateway:
Now you can use
ping to test if the gateway respond. This tool informs if a device with a given IP is answering. In plain English, with this test, we know that our network adapter, the cable and the router are connected correctly.
How to know if your dns is working
A DNS server is capable of converting a site name, for example www.maketecheasier.com, to its IP address. To connect to a computer in Internet, Windows needs that number. If you cannot connect to your DNS , it is almost impossible that Internet works.
As you can see in this case I have the same router and DNS IP address.
To test the DNS you can use
nslookup. This command make a query to that server. In the following image you can see how the server resolve Make Tech Easier address.
How to know if a process is opening too much connections
Every time a program needs to connect to Internet or other machine, it opens a new connection. A router can only handle a limited number of connection. If for any reason, a program opens many connections, you can end up with a block Internet.
We can do this with the command
netstat and the parameters “a” and “b”
You can see what programs are using these connections. In this case, you can see that I have a program named “Filezilla Server” listening in port 21.
How to check firewall rules
Firewall misconfiguration can lead to Internet malfunctioning. A firewall configuration is no more than a set of rules deciding whether an application can access the Internet or not. By default, these rules appear in abundance and you cannot see all of them in one screen. Instead, we can insert this information on a text file using the following commands:
The first command access the firewall configuration and write it to a text file. The second command open the text file in a new notepad window.
A basic use of the
netsh utility can inform us if there is one or more blocking rules to that use the command:
Unfortunately it doesn’t show what is the program blocked by that rule.
What other tricks do you use to test your internet connections?