How To Fix Network Problems Using Command Line Tools In Windows 7 2/2

Categories:  windows,
Labels:  OS, cmd, internet, network

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.

win7ci-cmd-ipconfig-all-dns-server

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.

win7ci-cmd-nslookup

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”

netstat -a -b

win7ci-cmd-netstat-ab

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:

netsh advfirewall firewall show rule name=all > firewallrules.txt
notepad firewallrules.txt

win7ci-cmd-notepad-firewallrules

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:

netsh advfirewall firewall show rule name | find "Block"

Unfortunately it doesn’t show what is the program blocked by that rule.

What other tricks do you use to test your internet connections?

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