What Is VPN Passthrough? How It Works and When to Use It
VPN passthrough is a router feature that you only really need if you’re using older VPN protocols. If you don’t, it won’t affect your router’s work in any way, but knowing what it does can help you recognize or troubleshoot issues when dealing with certain setups.
We’ll break down what VPN passthrough really means, why it exists, how it works on Linksys, Netgear, and other router types, and, most importantly, whether it’s relevant to you.
What Is VPN Passthrough?
A VPN passthrough allows a VPN connection to pass through your router’s firewall.
Your router’s firewall is designed to stop unfamiliar or unexpected data to protect your network. Most internet traffic follows a predictable pattern that your router expects. But some VPN protocols, especially older ones, send data in a way that looks unusual to the router; they use uncommon ports, skip standard headers, or heavily encrypt the traffic.
Because the router can’t make sense of this traffic, it blocks it. VPN passthrough is a built-in setting you can enable to let that traffic through.
It’s important to understand that VPN passthrough doesn’t mean the router is running the VPN itself. It just allows the VPN traffic from your devices to pass through and reach its destination.
How VPN Passthrough Works
To understand how VPN passthrough works, it helps to know how your router handles traffic using NAT (network address translation).
NAT allows all the devices connected to your network to use the same public IP address. It does this by keeping track of outgoing and incoming data using port numbers, which act like unique ID tags for each connection, so it knows which traffic belongs to which device.
For most online activities, like browsing, streaming, or gaming. NAT works seamlessly. Whether you’re using a laptop, phone, or game console, your router can forward the data to the right device without any issues.
The problem is that older VPN protocols such as PPTP, L2TP, and IPSec, weren’t designed with NAT in mind. Without a workaround, the router may block or misroute the VPN traffic, causing the connection to fail.
That’s where VPN passthrough comes in. When enabled, it tells the router to handle this unusual traffic differently. It creates exceptions so the VPN packets pass through the firewall and reach the correct device without being dropped or blocked. It doesn’t decrypt the data or interfere with your connection.
Types of VPN Passthrough
Not all VPN passthrough works the same way; different protocols require different processes.
- PPTP Passthrough: PPTP uses a protocol called GRE, which doesn’t support port numbers. Normally, the router handles this by tracking the control connection over TCP port 1723 and using a special Call ID inside GRE packets to match the session to the right device. But that’s not enough on its own. With passthrough enabled, the router is specifically configured to recognize and handle GRE traffic.
- IPSec Passthrough: IPSec uses its own protocols that don’t work well with NAT. Passthrough solves this by supporting NAT traversal (NAT-T), which wraps the encrypted IPSec traffic in standard UDP packets, making it easier for the router to process and forward.
- L2TP Passthrough: L2TP relies on UDP-based tunnels, and passthrough allows the router to recognize and manage those connections without dropping or misrouting the packets.
Do OpenVPN and WireGuard Need VPN Passthrough?
No, OpenVPN, WireGuard, and even IKEv2 are designed with NAT in mind, making the passthrough irrelevant.
OpenVPN uses standard TCP or UDP ports, which routers can easily recognize and manage. WireGuard, even though it’s newer, also uses standard UDP ports. As long as your router isn’t blocking the necessary ports, the traffic will go through just like any other internet data.
If you’re using PIA VPN, you can choose OpenVPN and WireGuard, so you won’t need VPN passthrough. The router treats your online traffic like any other encrypted connection and passes it along without an issue.
How to Enable VPN Passthrough
Most routers support VPN passthrough, but the steps to enable it vary between brands. If you can’t find it, a quick check of your router’s manual or a search for your model and “VPN passthrough” should point you in the right direction. Some routers may not even list it because it’s always enabled under the hood.
TP-Link, ASUS, & D-Link
Popular routers from TP-Link, ASUS, and D-Link have VPN passthrough in their settings. Often it’s under the Security, Firewall, or VPN sections of the admin interface. The wording might be Enable VPN Passthrough, or it might list the protocols individually.
Linksys
VPN passthrough on Linksys routers is usually in the Security tab of the admin interface. There are separate toggles for PPTP, L2TP, and IPSec passthrough. The default setting will typically have all three enabled. That means unless someone disabled them manually, your Linksys router is already set up for compatibility with VPNs.
Netgear
VPN passthrough on Netgear routers is automatic. There’s no setting to turn it on or off on most models; it’s designed to handle all VPN protocols. The firmware assumes that if a device is trying to initiate a VPN connection, the router should let it happen. In rare cases, if VPN traffic is blocked, you should double-check that NAT-T is working properly or look into setting up port forwarding. But for most users, it just works.
Is VPN Passthrough Secure?
VPN passthrough itself doesn’t weaken your network security. The passthrough feature simply allows the router to forward VPN traffic; it doesn’t decrypt or expose any of the encrypted data.
However, older protocols like PPTP that require passthrough aren’t as secure as the newer VPN protocols that don’t. So, even though the passthrough itself isn’t affecting your security, the fact that you need it means your connection might have vulnerabilities.
Alternatives to VPN Passthrough
If you’re having router issues because of VPN protocols that require passthrough, the best alternative is to get a VPN that uses modern protocols. PIA uses both OpenVPN and WireGuard for which you don’t need VPN Passthrough.
If that’s not an option, you can configure the VPN on your router and install compatible firmware like DD-WRT or OpenWrt to set up the router as the VPN client. This way, the router handles the VPN connection itself without needing passthrough.
Note that you can configure your router with PIA, too, and if you don’t want to deal with complex router configurations, you can purchase a FlashRouter with PIA pre-installed. This option requires almost zero setup – you plug it in, log in with your PIA credentials, and you’re good to go.
VPN Passthrough vs. Configuring a VPN on a Router
There’s a difference between the VPN passthrough and running a VPN directly on your router.
VPN passthrough only matters if your device, such as a laptop, phone, or streaming stick, is initiating the VPN connection. The router is just allowing that traffic to go out and come back in correctly.
If you’ve set up a VPN client on your router itself, the passthrough setting becomes irrelevant. In that case, the router is the one connecting to the VPN server, so it doesn’t need to “pass through” anything. It’s the starting point of the connection, not a gatekeeper.
Turning your router into a VPN client requires more advanced configuration, but it eliminates the need for passthrough. It also allows you to connect all the devices on your home network, including a smart TV, without installing a VPN app on each device.
Do You Need VPN Passthrough With PIA?
Usually not. All PIA VPN apps include WireGuard and OpenVPN, which are NAT-friendly protocols. So whether you download the PIA VPN app directly on your device or configure your router to run the VPN directly, PIA will connect just fine.
PIA does support IKEv2/IPSec on iOS, so you might need VPN passthrough if you’re using that protocol, but it’s rarely necessary for typical setups. Your VPN might not connect or drop frequently over that protocol if your router blocks ESP traffic or UDP ports 500 and 4500, which is more common on older routers.
And if you’re not using a VPN at all? The setting won’t hurt anything if it’s enabled, but there’s no reason to keep it on either.
Here’s the bottom line: VPN passthrough is a legacy compatibility feature that only matters in specific situations. Most of the time, you won’t need it. But if you do, it’s good to know what it does and how to turn it on.
FAQ
There’s no reason to disable the VPN passthrough on your router. It’s a compatibility feature that’s only relevant with certain VPN protocols like PPTP, L2TP, or IPSec. If your VPN uses OpenVPN or WireGuard, the setting won’t affect you.
When a router lists VPN passthrough only, it means the router itself doesn’t act as a VPN client or server but allows VPN traffic from devices on your network to pass through. Essentially, the router isn’t creating the VPN connection it’s just making sure it doesn’t block or interfere with VPN traffic.
VPN passthrough allows the router to recognize and handle VPN traffic that would normally be blocked by its NAT firewall. For PPTP, L2TP, and IPSec, the router uses specific methods to track session details or support NAT traversal. This ensures that incoming and outgoing VPN packets reach the right device on your network.
VPN passthrough is primarily needed for older protocols like PPTP, L2TP, and IPSec. These protocols weren’t designed with NAT in mind and need special handling to pass through a router’s firewall.
If VPN passthrough is disabled and you’re using a VPN with IPSec, PPTP, or L2TP, your router’s NAT firewall may block or drop the VPN traffic. This can prevent your device from establishing a VPN connection entirely. You might see repeated connection errors or find the VPN tunnel fails during setup.
You can typically enable VPN passthrough by logging into your router’s admin interface and navigating to the Security or Firewall settings. Look for specific toggles labeled PPTP, L2TP, or IPSec passthrough and make sure they’re turned on. On some routers, passthrough is always enabled and doesn’t require a manual setting.
VPN passthrough doesn’t have an impact on the connection speed or stability. It simply allows specific VPN traffic types to pass through the router without being blocked.
No, you don’t need VPN passthrough for all types of VPNs. VPN protocols like OpenVPN and WireGuard work without special configuration. VPN passthrough mainly applies to older protocols that struggle with NAT, such as PPTP, L2TP, and IPSec.