What Is VPN Passthrough? [Why & When To Use It]

VPN passthrough is a feature that allows a device connected to your VPN to go through your router’s firewall. It enables users to connect to a VPN server from behind a firewall. 

If your router does not support VPN passthrough or has it disabled, your VPN traffic will be blocked. The feature is especially important when dealing with NAT (Network Address Translation) routers, commonly used to manage internal IP addresses in corporate environments. 

How a VPN passthrough works

Imagine you are working from home and need to access the company’s internal network. Your connection passes through your home router, which typically uses NAT. 

Without a VPN passthrough, your VPN client might struggle to establish a connection because the VPN protocols are blocked or not recognized properly. This is where VPN passthrough comes into play. It ensures that protocols like PPTP, L2TP, and IPsec do not face interference and can traverse the NAT router without issues.

Suppose also that you are using an IPsec VPN to connect to the corporate server. Your corporate firewall needs to be configured to allow IPsec passthrough. Here’s a simplified configuration snippet for an IPsec VPN setup on a firewall using iptables:

This configuration snippet ensures that the key protocols used by IPsec VPNs are not blocked by the corporate firewall. It’s small configurations like these that allow users to work securely from anywhere without the headache of connection problems.

Another scenario where VPN passthrough is vital involves employees traveling abroad. If your sales executive who is traveling internationally needs access to sensitive data on your internal servers, VPN passthrough will ensure they establish VPN connections and carry on with their work, even with the strict NAT configurations of their hotel’s network.

By ensuring VPN passthrough is enabled on your network devices, you keep your remote workforce connected and secure. This VPN feature ensures that your security measures, important as they are, do not become obstacles but rather enablers of efficient and secure work. 

Advantages of VPN passthrough on corporate network connectivity

Enhanced security

VPN passthrough isn't just a gateway for bypassing firewalls; it’s a security enhancer. It ensures that your encrypted data remains secure without exposing your network to vulnerabilities. 

If you’re working from a remote location and need to access your company’s internal servers securely, without VPN passthrough, your firewall might block these encrypted connections, thinking they're suspicious. 

However, with VPN passthrough enabled, your firewall allows these secure packets to pass through without decrypting them, maintaining a secure channel. This setup is particularly crucial when utilizing protocols like IPsec, PPTP, or L2TP that are designed to provide secure tunneling and data integrity. 

Moreover, VPN passthrough is backward-friendly. Some older VPN clients might not handle NAT (Network Address Translation) very well. VPN passthrough helps these older clients to connect smoothly by allowing encrypted traffic via NAT without breaking the VPN tunnel.

Protection of sensitive data

Generally, a VPN enhances security by hiding your IP address and browsing activity from hackers and encrypting your data. Therefore, by allowing VPN traffic to freely pass through a router, VPN passthrough adds an extra layer of security.

Assume that you're sending confidential financial reports back to headquarters. Without VPN passthrough, your VPN connection might drop, leaving your data exposed. But with VPN passthrough enabled, your secure tunnel remains intact, keeping sensitive information safe.

Another example involves remote desktop access. Suppose you're an IT administrator trying to troubleshoot the VP of marketing’s laptop. With VPN passthrough, your VPN connection remains robust, allowing you uninterrupted access to the device. This makes solving technical issues quicker and more secure.

By keeping your VPN connection stable through VPN Passthrough, you significantly enhance the security of your data transmissions. Whether it's client information, internal emails, or financial data, everything sent over the VPN connection is encrypted and protected.

Secure remote access for employees 

A VPN (Virtual Private Network) is essential for this for remote employees who need to connect to your company's internal network. It creates a secure tunnel between your device and the corporate network, keeping your data safe from prying eyes.

VPN passthrough ensures that your router won't interfere with the encrypted data moving through it. This significantly enhances your corporate network security while offering flexibility for remote work.

Implementing VPN Passthrough in a corporate Network

To implement VPN Passthrough in a corporate network, your router must support VPN Passthrough. The good thing is almost all modern routers do. If you are unsure that your router supports the feature, you can usually find this information in your router's manual or on the manufacturer's website.

To enable VPN Passthrough on a router like the Netgear Nighthawk, you'll need to log in to its web interface. Open your browser and type in your router’s IP address. For the Nighthawk, this is typically `http://192.168.1.1`. Enter your admin credentials to access the settings.

Once you're logged in, navigate to the "Advanced" tab. Under the "Setup" section, look for "WAN Setup." Here, you'll see options for enabling VPN Passthrough for different protocols such as PPTP, L2TP, and IPSec. Enable the ones that your corporate VPN uses. Lastly, you need to configure the VPN client software on your employees' devices.