FTP Active vs Passive: Which is Better?

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You may have experienced the slow or unreliable FTP connection, and want to know what is the reason right? There are 2 modes for FTP active vs passive and the FTP issues can be due to these modes. Both of them have similar goals, but there are differences between them in the case of managing connections. The conventional approach, active FTP, requires the client to initiate a connection to the server via a specific port. However, many users now choose passive FTP because it reverses the connection paradigm, with the server taking the initiative to connect to the client on a randomly selected port. But is passive FTP truly a better option just because it is newer? FTP passive vs active which is better? Continue reading to find out the answers to these questions.

Why FTP is Still Important?

The fact that FTP is old, is not a reason that it is unusable. Despite its age, FTP still remains a valuable file transfer technology due to its simplicity, reliability, and versatility. It's a simple protocol that has repeatedly been proven to guarantee reliable file transfers. Another benefit of FTP is its capacity to handle huge files. Unlike email, which often has size limitations, FTP can transfer files of almost any kind easily. Scheduling and automation increase FTP's utility. Many FTP systems allow users to automate file transfers, guaranteeing that files are relocated or duplicated at certain times or under specified conditions.

What is active mode FTP?

FTP`s older versions always use only one data connection to run, which is named active mode. This is the default mode in many FTP software. Active mode FTP is an easy technique for computers to transfer files. It's similar to calling a friend on a cellphone. You call them at a specified number (the server's port). Then you want them to call you back at another number (the client's port). The second call is used to transfer the files. Here we show you how an active mode of FTP works:

The client calls the server: The computer attempting to access the files (the client) contacts the server via a FTP port number (21).
The server calls back: The server instructs the client to call back using a different port number.
The client calls back: The client dials the server again at the new number. This is where the real file transfer occurs.

What is passive mode FTP?

Passive mode FTP is a modern method for computers to transmit files and create data connections. It's similar to calling a friend, but instead of them calling you back, you call them at the number they gave you. As mentioned before, earlier systems only support active mode; however, more contemporary systems, including modern GUI-based or command-line FTP clients, also support passive mode. In passive mode, the client begins the conversation rather than the server. The passive mode works like this:

The client dials the server: The computer attempting to access the files (the client) contacts the server via a unique port number (21).

The client instructs the server to operate in passive mode: The client instructs the server to use passive mode for file transfers.

The server gives the client a number: The server provides the client with a different port number to call.

The client calls the server back: The client dials the server again at the new number. This is where the actual file transfer occurs.

Firewall considerations for a seamless connection

Firewalls can sometimes interfere with FTP connections. We recently observed which computer (the client or the server) starts the connection. This can affect how the firewall reacts.

Client-side firewalls

Firewalls often place more restrictions on connections coming in (inbound) than connections going out (outbound). This can interfere with FTP connections. If you have a firewall on your system (client-side firewall) and attempt to connect to an FTP server, the firewall will most likely allow you to connect. This is because you are beginning the connection (outbound).

All FTP connections to the server (control connections) are outgoing from your PC. You need to be able to connect to the server without issue. However, this may not be the case with the data connection.
If you use active mode FTP, the server will attempt to connect to your system (an inbound connection). This may be prevented by your firewall.

If you're having problems connecting to an FTP server, look in the server logs to determine if the initial connection (control connection) was successful. If it was, check to see if the client is operating in active mode.

If the client is in active mode, your computer's firewall may be obstructing the data connection. This can happen with any firewall, but since the majority of users use Windows, you should first check your Windows firewall. Passive mode FTP is less likely to cause issues with firewalls. In passive mode, your computer initiates both the initial and data connections (outbound). So, your firewall should accept both.

Server-side firewalls

Server-side firewalls are also required for FTP connections. When you set up an FTP server, make sure your firewall allows other computers (clients) to connect to it. To allow the initial connection (command channel), you must open port 21 on your firewall. This will allow clients to connect to your server and initiate an FTP session.

For active mode FTP, the server initiates a data connection. This is an outgoing connection from the server, thus your firewall should allow it. For passive mode FTP, the client initiates the data connection. This is an incoming connection to the server, thus your firewall may block it. To allow this, you must open a number of ports on your firewall. This will allow clients to connect to the server for the data transfer.

What are the Differences between FTP Active vs Passive?

The main difference between FTP active vs passive is who starts the data connection. In Active FTP, the server starts the data transfer, while in Passive FTP, the client takes the lead. This affects security and firewall functionality. Now, let`s explore the differences between FTP Active vs Passive in more detail.

Security Considerations

Active FTP: The security of active FTP is lower and it is easier for attackers to target it because of the fixed server ports (21 for command and 20 for data).

Passive FTP: The random data port on the server in passive FTP makes it more difficult to intercept transmissions of data. Passive mode, on the other hand, forces the server to open additional ports, which may result in holes in the system.

Firewall Compatibility

Active FTP: Client-side firewalls often block the server's data-in connection, causing potential problems.

Passive FTP: The client starts both the command and data connections, making it more suitable for client-side firewalls. However, server-side firewalls may still block inbound data connections in Passive mode.

Command and Data Channels

Active FTP:

Client's command and data ports are random.
Server's command port is 21, and data port is 20.

Passive FTP:

Client's command and data ports are random.
Server's command port is 21, and data port is also random.

Reasons to Use FTP Active vs passive

Each provide pros and cons and before choosing, you should consider what you need.

Reasons to Use Active FTP

Easy to Use: Active mode usually serves as the default and can be easier to configure in some situations.
Firewall connection: In certain network situations, Active mode may be more compatible with server-side firewalls because of the outgoing data connection.

Reasons to Use Passive FTP

Security: Passive mode improves security by randomly selecting the data port. As a result, it is more difficult for attackers to target.
Client-side firewall connection: Passive mode is more compatible with client-side firewalls because the client initiates both command and data connections.
Flexibility: In passive mode, you can define a variety of data connection ports, providing you with more choice over your network design.

Command Prompt FTP Support

The Windows Command Prompt FTP client supports just Active FTP; it does not support Passive mode. If you need to use Passive FTP, you'll need to use a client like WinSCP or another command-line client that supports Passive mode.

Why Do Two FTP Modes Exist?

Now that you know the differences between Active and Passive FTP modes, you may want to know why both are needed. The answer is in how firewalls handle these connections.

Active Mode Challenges: In Active mode, the server starts the connection with the client. While the client understands which port the server will use, the client's firewall may block the connection since it is uninformed of the incoming request.
Passive Mode Solution: Passive mode addresses this by requiring the client to start both connections to the server over a port provided by the server. However, the server's firewall may continue to deny the connection for similar reasons.

The two approaches exist to solve these firewall difficulties in different ways.

Is Windows 7 FTP Server Active or Passive?

Windows 7 users can set up an FTP server using IIS (Internet Information Services). IIS supports Active and Passive FTP by default. While no special mode needs to be activated by hand, you can adjust the passive port range in IIS settings if necessary.

Do Web Browsers Support Active or Passive FTP Modes?

Web browsers such as Chrome and Firefox use your operating system's network settings to decide whether to use Active or Passive FTP. Most Windows systems use Passive FTP by default since it is more friendly with firewalls. To enable or disable passive mode in browsers:

To access the Windows search, use 'WinKey + S'.
Type and select "Internet Options".
In the "Internet Properties" window, select the "Advanced" tab.
Scroll to the Browsing section.
Check or uncheck the option labeled "Use Passive FTP (for firewall and DSL modem compatibility)."
Click OK to make the changes.

How to Switch from Active to Passive FTP?

To switch from active to passive FTP in FileZilla:

Open FileZilla.
Go to settings: Click "Edit" in the menu bar, then "Settings."
Open FTP Settings: In the Settings panel, select "Connections" and then "FTP."
Select Passive mode: Choose "Passive (recommended)" from the "Transfer Mode" options.
Save your changes: Click "OK" to save your changes.

FTP passive vs active which is better?

Now that you know everything about them, the question is FTP passive vs active which is better? The crux of the issue lies in how firewalls interact with these modes. In active mode, a client-side firewall frequently blocks outbound connections to random ports, preventing the server from reconnecting. This can cause connection troubles. On the other hand, in passive mode, a server-side firewall can block inbound connections to arbitrary ports, preventing the client from connecting to the server. This can also cause connection troubles.

While firewalls effect both modes, there`s still a big difference between them: controlling over firewalls! In most of the situations, you have more control over your server-side firewall than over your client's firewall, especially when you're providing FTP services to external clients. That`s why passive mode can be a better option. So, when you ask “FTP passive vs active which is better” we can say the passive mode is generally preferred due to:

Better control: By setting your server-side firewall to enable inbound connections on the appropriate ports, you can decrease the chance of connection problems.
Lower complexity: Managing security rules on your server is often easier than working with clients to adjust their firewalls.

Better compatibility: Passive Mode can often be more compatible with different network settings, particularly those with stringent firewalls.

Security Tips for Passive FTP Configuration

There are some security considerations for configuring passive FTP that you should be aware. Here are some security tips:

Specify a Port Range: Rather than opening random ports, your FTP server should use a particular range of ports for passive mode data connections.
Open the same range on the firewall: Allow just the same range of ports on your firewall that you have set up for passive mode on the FTP server.
Minimize security risks: This method minimizes the attack surface by minimizing the number of exposed ports.
Enable the necessary FTP connections: While increasing security, make sure that legal FTP connections can still be made.

Conclusion

FTP Active vs Passive uses various connection processes, each having pros and cons. The best option is based on what you want. In this review, we've also answered some typical questions concerning both types. While both have their merits, Passive Mode is typically the most practical and dependable option, particularly when working with external clients or in complex network setups. Understanding firewall behavior and using Passive Mode can improve the dependability and accessibility of your FTP services.

Category: Networking