RDP Protocol: Key Settings and Common Connection Errors

The RDP protocol (Remote Desktop Protocol) is a proprietary protocol developed by Microsoft that allows users to remotely connect to and control another computer over a network. It is widely used by businesses and IT administrators to provide remote access to servers, computers, or virtual machines. RDP makes it possible to perform tasks on a remote machine as if you were sitting in front of it, making it a valuable tool for remote work and technical support.

In this article, we’ll explore the basic settings of the RDP protocol, how to configure it properly, and address common connection errors that users may encounter.

What is RDP (Remote Desktop Protocol)?

RDP is a network communication protocol that enables remote access to a computer’s desktop environment. Using RDP, users can interact with a remote machine as if they were using it locally, with access to files, applications, and network resources. RDP is especially useful for system administration, troubleshooting, and remote technical support.

The RDP protocol works over TCP port 3389 by default, and Microsoft provides the Remote Desktop client application on Windows, macOS, Android, and iOS, allowing users to connect to RDP-enabled computers.

Key RDP Settings

Configuring RDP properly is essential to ensure a smooth and secure connection. Below are the key settings to consider when setting up RDP.

1. Enable Remote Desktop

Before using RDP, you need to enable Remote Desktop on the remote machine. This is the first step to allowing remote connections.

Steps to Enable Remote Desktop (Windows 10/11):

1. Open Settings and go to System.
2. Select Remote Desktop from the left-hand menu.
3. Toggle Enable Remote Desktop to On.
4. Confirm the action and take note of the computer’s name, as you’ll need it to connect.

2. Firewall Settings

By default, the Windows Firewall blocks RDP connections. You need to allow the Remote Desktop app through the firewall to enable successful connections.

Steps to Configure the Firewall:

1. Open Windows Defender Firewall from the Control Panel.
2. Click on Allow an app or feature through Windows Defender Firewall.
3. Find and check the box next to Remote Desktop for both Private and Public networks.

3. RDP Port Configuration

RDP uses TCP port 3389 by default. If you want to increase security by changing the port or if port 3389 is already in use, you can modify the port in the Windows Registry.

Steps to Change the RDP Port:

1. Press Windows + R, type regedit, and press Enter to open the Registry Editor.
2. Navigate to the following key:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp\PortNumber
3. Right-click on PortNumber, select Modify, and change the value to a new port number (e.g., 3390).
4. Restart the computer for the changes to take effect.

4. User Permissions

Only users with appropriate permissions can access a remote computer via RDP. You need to ensure that the correct user accounts have permission to connect.

Steps to Add Users for Remote Access:

1. Go to Control Panel > System and Security > System.
2. Click on Remote settings.
3. Under Remote Desktop, click Select Users.
4. Click Add and type the names of the users who should have remote access.

5. Network Level Authentication (NLA)

Network Level Authentication (NLA) adds a layer of security by requiring users to authenticate before a full RDP session is established. It helps protect against unauthorized access and denial-of-service attacks.

Steps to Enable NLA:

1. Go to Control Panel > System and Security > System.
2. Click Remote settings on the left.
3. Under the Remote Desktop section, check the box for Allow connections only from computers running Remote Desktop with Network Level Authentication (recommended).

Common RDP Connection Errors and How to Fix Them

When using RDP, you may encounter several connection issues. Below are some common RDP errors and their solutions.

1. “Remote Desktop Can’t Connect to the Remote Computer”

This error typically occurs due to network problems, incorrect configuration, or firewall restrictions.

Solutions:

• Ensure the remote computer is turned on and connected to the network.
• Verify that the Remote Desktop feature is enabled on the remote machine.
• Check the firewall settings to ensure that RDP traffic is allowed.
• Confirm that the correct IP address or hostname is being used to connect.

2. “The Credentials That Were Used to Connect Are Incorrect”

This error usually occurs when the user enters the wrong login credentials, or there are issues with domain authentication.

Solutions:

• Verify the username and password are correct, including any domain name if necessary.
• If using Network Level Authentication (NLA), ensure the user account has permission to connect remotely.

3. “Remote Desktop Connection Timed Out”

This error indicates a network issue or a firewall blocking the RDP connection.

Solutions:

• Check network connectivity on both the client and the server.
• Verify that the RDP port (default 3389) is open on the router and firewall.
• Ensure the correct IP address or domain is being used.
• Try increasing the connection timeout settings in the Remote Desktop client by editing the Timeout registry values.

4. “The Remote Desktop Session Has Ended”

This error can happen if the RDP session is abruptly disconnected due to network instability or an issue with the remote server.

Solutions:

• Check the network connection on both the client and server sides to ensure stability.
• Ensure that the remote machine is not going into sleep or hibernate mode, which can disconnect active RDP sessions.
• Check for resource limits on the server (e.g., if multiple users are connected).

5. “Your Remote Desktop Connection Failed Because the Remote Computer Cannot Be Authenticated”

This error typically occurs when there’s a mismatch between the security certificate used by the server and what the client expects.

Solutions:

• If you trust the remote server, check the box Don’t ask me again for connections to this computer and click Yes when the warning appears.
• Verify that the SSL certificate on the remote server is properly configured.

Best Practices for Securing RDP Connections

While RDP is a powerful tool, it is often targeted by attackers due to its remote access capabilities. Here are some best practices for securing your RDP connections:

1. Use a VPN

Whenever possible, connect to remote computers via VPN (Virtual Private Network). This adds an extra layer of security by encrypting the connection before accessing the remote desktop.

2. Change the Default RDP Port

Changing the default RDP port from 3389 to a non-standard port helps reduce the risk of automated attacks that scan for open RDP ports.

3. Enable Two-Factor Authentication

For an added layer of security, enable two-factor authentication (2FA) for RDP access. Some services, such as Microsoft Azure, allow 2FA for RDP sessions.

4. Limit RDP Users

Only provide RDP access to users who absolutely need it. Use the principle of least privilege, ensuring that only specific user accounts can log in remotely.

5. Use Strong Passwords

Ensure that all user accounts allowed to access RDP have strong, complex passwords to prevent brute-force attacks.

Conclusion

The RDP protocol is a highly useful tool for remote desktop access, making it possible to work on or manage computers from a distance. By understanding the key settings, such as enabling Remote Desktop, configuring firewall rules, and using Network Level Authentication (NLA), you can ensure a secure and stable RDP experience. Additionally, knowing how to troubleshoot common RDP connection errors will help you resolve issues and keep your remote operations running smoothly. By following best security practices, you can also protect your systems from unauthorized access and potential security threats.