Checking Network Connections on Windows Servers

When you're managing Windows servers, being able to quickly check network connections is essential. This helps in troubleshooting issues like applications not connecting, or services not communicating. We'll look at some straightforward commands to help you diagnose these problems.

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TESTING SPECIFIC CONNECTIONS (PowerShell)

The Test-NetConnection command is a powerful tool in PowerShell for checking connectivity to a specific IP address and port.

• How to use it:

  test-netconnection IPAddress -port XXXXX

• Replace IPAddress with the actual IP address of the server you're trying to reach.

• Replace XXXXX with the specific port number that the service (like a license server) is listening on.

This command will tell you if a connection can be established, making it great for verifying if a service is reachable on a particular port.

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USING TELNET FOR BASIC CONNECTIVITY

Telnet is a simple command-line tool that can test connectivity to a port. It's often used to see if a port is open and listening.

• ENABLING TELNET CLIENT

  By default, the Telnet Client might not be installed on Windows Server. You need to enable it first.

  dism /online /Enable-Feature /FeatureName:TelnetClient

  This command uses DISM (Deployment Image Servicing and Management) to add the Telnet Client feature.

• TESTING WITH TELNET

  Once enabled, you can use Telnet to test a connection.

  telnet -a IPAddress XXXXX

  Again, replace IPAddress with the target server's IP and XXXXX with the port. If you see a blank screen or a connection successful message, it usually means the port is open. If it fails quickly, the port might be blocked or the service isn't running.

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VIEWING ACTIVE NETWORK CONNECTIONS (NETSTAT)

netstat is a command-line utility that displays active network connections, routing tables, and a number of network interface statistics. It's great for seeing what your server is connected to, and what ports it's listening on.

• SHOW ALL CONNECTIONS AND LISTENING PORTS

  netstat -a

  This command will list all active TCP connections and the TCP and UDP ports on which the computer is listening.

• SHOW NUMERICAL ADDRESSES AND PORT NUMBERS

  netstat -n

  This variation shows addresses and port numbers in their numerical form, which can be quicker and avoid DNS lookups.

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MANAGING WINDOWS FIREWALL (NETSH ADVFIREWALL)

The Windows Firewall can often be the reason why connections aren't working. The netsh advfirewall command allows you to view and manage firewall settings.

• SHOW ALL FIREWALL PROFILES

  netsh advfirewall show allprofiles

  This command displays the settings for all firewall profiles (Domain, Private, and Public).

• CHECK SPECIFIC FIREWALL PROFILES

  You can check the status of individual profiles:

  netsh advfirewall show domainprofile

  netsh advfirewall show privateprofile

  netsh advfirewall show publicprofile

  These commands show the specific settings for the domain, private, or public network profiles respectively.

• CHANGE FIREWALL PROFILE STATE

  You can enable or disable firewall profiles if needed, though this should be done with caution.

  netsh advfirewall set allprofiles state [on/off]

  Replace [on/off] with on to enable or off to disable all profiles.

Streamlining IP Address Management on Windows Servers

Managing multiple IP addresses on a Windows server through the graphical interface can be a tedious process, requiring manual entry for each IP address in separate dialog boxes. However, there's a much simpler solution that allows you to add entire subnets in seconds using the command line.

Adding IP Addresses from the Command Line

Windows provides the netsh command, enabling configuration of network connections. To add an IP address, use the following syntax:

netsh interface ipv4 add address "Local Area Connection" 192.168.1.2 255.255.255.0

This command adds the IP address 192.168.1.2 with subnet mask 255.255.255.0 to the connection titled "Local Area Network."

Adding Multiple IP Addresses at Once

By combining the netsh command with a FOR /L loop, you can quickly add multiple IP addresses. The syntax for the loop is:

FOR /L %variable IN (start,step,end) DO command

To add every IP address from an entire subnet, use:

FOR /L %A IN (0,1,255) DO netsh interface ipv4 add address "Local Area Connection" 192.168.1.%A 255.255.255.0

This command efficiently adds all IP addresses from 192.168.1.0 to 192.168.1.255 to the "Local Area Connection" interface.

Quick Demonstration

To illustrate, let's add IP addresses 192.168.1.10 to 192.168.1.20:

FOR /L %A IN (10,1,20) DO netsh interface ipv4 add address "Local Area Connection" 192.168.1.%A 255.255.255.0

After running the command, the IP Configuration of the adapter displays the new addresses.

Additional Commands

Here are some useful additional netsh commands:

• To list IP addresses: netsh int ipv4 show ipaddresses level=verbose
• To delete an IP address: netsh int ipv4 delete address "Local Area Connection 1" 10.114.1.35

Adding IP Addresses to Your Dedicated Windows Server

For Windows Server 2003 and earlier:

1. Log in to Remote Desktop.
2. Navigate to Control Panel -> Network Connections -> Local Area Connection.
3. Right-click Properties -> Internet Protocol (TCP/IP) -> Properties -> Advanced -> Add.

For Windows Server 2008:

1. Log in to Remote Desktop.
2. Open the Start menu and select Network.
3. Double-click Network and Sharing Center.
4. Click Change Adapter Settings -> Right-click server's network card -> Properties.
5. Select Internet Protocol Version 4 (TCP/IPv4) -> Properties -> Advanced -> Add.

Understanding and Editing the Hosts File

Introduction:

The hosts file is a simple text file that maps hostnames to IP addresses. It allows a computer to resolve hostnames to IP addresses before it queries a DNS server. This file is available on various operating systems with similar but slightly varying paths and is particularly useful for redirecting traffic, testing websites before DNS changes, or blocking unwanted sites.

Here's a brief guide on the hosts file, its location across different operating systems, and how to edit it.

Understanding the Hosts File

The hosts file contains lines of text consisting of an IP address in the first text field followed by one or more hostnames. Each field is separated by white space (tabs are often preferred for historical reasons, but spaces are also used).

Example entry:

127.0.0.1    localhost

Hosts File Location

• Windows 95/98/Me: C:\Windows\hosts
• Windows NT/2000/XP: C:\windows\system32\drivers\etc\hosts or C:\winnt\system32\drivers\etc\hosts
• Windows 7/8/10/11: C:\windows\system32\drivers\etc\hosts or use %systemroot%\system32\drivers\etc\hosts
• Linux/Unix/Mac OS X: /etc/hosts

Note: Windows users may need to open Notepad as an Administrator to edit the file.

Editing the Hosts File

Windows:

1. Open Notepad as Administrator: Right-click on Notepad and select "Run as Administrator".
2. Open the Hosts File: In Notepad, go to File -> Open and navigate to C:\Windows\System32\drivers\etc. Change the file filter to "All Files" and open the hosts file.
3. Edit and Save: Add your new entries. Save the file when done.

Linux/Unix/OS X:

1. Open Terminal: You will need root access to edit the hosts file.
2. Edit the Hosts File: Use a text editor like nano or vi. For example: sudo nano /etc/hosts.
3. Edit and Save: Add your new entries. Save and exit the editor.

Common Entries:

• Loopback Address: 127.0.0.1 is usually associated with the hostname localhost and is used to point back to your own machine.
• Blocking Websites: To block a website, you might add an entry like
• 127.0.0.1 unwanted-website.com.
• Development Purposes: Redirect a domain to your local machine for development by adding an entry like
• 

• 127.0.0.1 my-website.dev.

Testing Changes:

After saving changes to your hosts file, you can test them by pinging the hostname you added:

• Windows/Linux/Unix/OS X: Open your command prompt or terminal and type ping hostname (replace hostname with the one you added).

Conclusion:

Editing the hosts file is a powerful way to control how your system resolves hostnames. It's used by system administrators for testing, by developers for routing traffic to local development environments, and can even be used to block malicious or unwanted websites. Remember to back up the original file before making changes and ensure that you understand the implications of any modifications you make.