If you’re struggling to connect to your work VPN, or it keeps dropping without any apparent reason, the problem might not even be with your VPN app. It may be a little-known router setting known as VPN passthrough.

It’s a rarely touched feature. And many people don’t know about it. But if it’s not set up properly or is turned off, your work VPN won’t work.

But what is VPN passthrough, why is it important, and what can you do about it?

We’ll explain it in plain English.

What is VPN Passthrough?

VPN passthrough is a router setting that ensures traffic from your VPN will pass through your router’s firewall and network address translation (NAT) system.

Put simply, it’s a sort of “permission slip” that your router has, saying:

“Let this encrypted VPN traffic pass through unhindered.”

If you don’t have it, your router could interpret the VPN data as something else, and block it.

That’s why many people who search “pass through VPN not working” have a passthrough problem, rather than a VPN problem.

Understanding NAT Passthrough and why it matters

VPN passthrough is a term that refers to Network Address Translation (NAT).

NAT allows your router to connect multiple computers in your home to the internet with a single public IP address.

NATs are necessary, but they can also cause VPNs to not work properly - particularly older VPNs.

This is where NAT passthrough (also known as network passthrough) comes in.

What is NAT passthrough?

NAT passthrough is what allows certain kinds of traffic, such as VPN packets, to pass through the NAT so the connection works.

Without NAT passthrough:

  • VPN packets may get dropped
  • Establishing connections might be difficult
  • Work VPNs may disconnect frequently

What is IP passthrough?

IP passthrough is a little different. Rather than just letting other traffic through, it maps your router’s public IP address to a single device on your network.

Think of it like:

  • VPN passthrough → allows VPN traffic
  • IP passthrough → allows a device to be recognized on the internet

IP passthrough is often used in advanced networks such as:

  • Business routers
  • Double-router networks
  • Modem + separate router

How VPN Passthrough works

Your router has a firewall that restricts traffic.

The majority of internet traffic is routine. But VPN protocols - particularly older versions - do not.

For example:

  • They use unusual ports
  • They encrypt data differently
  • They may not have certain headers

This means that they’re often blocked by default.

VPN passthrough overcomes this by:

  • Recognizing VPN-specific traffic
  • Allowing it through the firewall
  • Preventing NAT conflicts

This allows your computer to connect to an external VPN server.

VPN Passthrough

Routers typically have multiple passthroughs.

Here are the most common:

PPTP Passthrough

  • One of the original VPN protocols
  • Commonly employed in older enterprise networks
  • Needs passthrough as it doesn’t play well with NAT

L2TP Passthrough

  • Newer than PPTP
  • Used in legacy enterprise VPNs
  • Requires passthrough for routing

IPSec Passthrough

  • Commonly used in corporate VPNs
  • Better security than PPTP and L2TP
  • Used with NAT traversal (NAT-T)

On your router, you can normally turn each on/off:

  • PPTP passthrough
  • L2TP passthrough
  • IPSec passthrough

IPSec passthrough: on or off?

The answer: ON (most of the time).

If you’re using IPSec for work VPN (and many do), turning this off will probably disconnect you.

IPSec has trouble with NAT, and needs passthrough to work around this.

Turn it OFF only if:

  • You don’t use a VPN
  • You need to troubleshoot something
  • You’re prompted by your router firmware

Why your work VPN is not working

If you use a VPN to connect to the office and it isn’t working, VPN passthrough may be the culprit.

Here’s what typically happens:

Scenario:

  • You start your company VPN
  • It tries to connect
  • It can’t connect or times out

What’s actually happening:

  • VPN traffic is filtered by your router
  • NAT interferes with the protocol
  • VPN cannot complete the handshake

Some VPN protocols won’t work without passthrough.

“Netgear Nighthawk VPN passthrough not working.”

On Netgear routers:

  • VPN passthrough is typically enabled by default

It can be found under:

Advanced Settings → WAN Setup

Make sure:

  • PPTP passthrough = enabled
  • L2TP passthrough = enabled
  • IPSec passthrough = enabled

If your work VPN still fails:

  • Restart router
  • Update firmware
  • Turn off SIP ALG (another common problem)

Do you need VPN Passthrough?

Here’s the interesting thing:

Most VPNs don’t require it.

Newer protocols like:

  • OpenVPN
  • WireGuard
  • IKEv2

automatically work with NAT.

Then, when or why do you need passthrough?

You need it if:

  • Your organization uses legacy VPN protocols
  • You have manually set up PPTP, L2TP, or IPSec
  • Your VPN is not working with a router

VPN Passthrough vs VPN Router

A common misunderstanding:

VPN passthrough ≠ VPN router

VPN passthrough:

  • Does NOT establish a VPN
  • Only allows traffic to pass through
  • Uses VPN apps on your device

VPN router:

  • Establishes the VPN connection
  • Secures the whole network
  • Requires configuration

This can result in people turning passthrough on and expecting encryption - when there will be none. For this reason, users also often ask can a VPN bypass WiFi restrictions, as a VPN (unlike passthrough) can route your traffic and can use remote servers.

Users also often ask, does a VPN protect you from viruses but a VPN is only designed to encrypt your internet traffic, not protect you from viruses

With VPN passthrough turned OFF you could experience:

  • VPN not connecting
  • Frequent disconnects
  • “Timeout” or “authentication failed” errors
  • Unable to connect to corporate servers
  • VPN performance problems

Such problems are particularly prevalent with:

  • Work-from-home setups
  • University networks
  • ISP-provided routers

How to turn VPN Passthrough on

The process will vary from router to router, but it’s something like:

  1. Access your router settings - usually 192.168.0.1 or 192.168.1.1
  2. Enter your login details
  3. Go to:
    • Advanced Settings
    • Security
    • WAN or Firewall
  4. Locate VPN Passthrough
  5. Enable:
    • PPTP passthrough
    • L2TP passthrough
    • IPSec passthrough
  6. Save and reboot router

Security concern that should be considered

It’s important to understand broader cybersecurity practices, as VPN passthrough is only one aspect of network security.

Is VPN passthrough safe?

Generally, yes.

It doesn’t:

  • Expose your network
  • Create vulnerabilities
  • Replace encryption

It just permits encrypted VPN traffic to flow.

However:

  • PPTP is insecure and old
  • IPSec and others are more secure

Conclusion

VPN passthrough is a hidden setting that you usually don’t think about, but can be a real work-stopping setting if it goes wrong.

The bottom line is:

  • If your VPN works → don’t change it
  • If your VPN doesn’t work → try passthrough

Knowing what is VPN passthrough, what IP passthrough is, and how NAT passthrough works can help you avoid hours of headaches - especially when you’re working remotely.

FAQs

What is VPN passthrough?

A feature of a router that makes VPN traffic pass through NAT and firewalls.

What is IP passthrough?

A feature that assigns your router’s WAN IP address to a single device.

What is NAT passthrough?

A feature that lets VPN traffic through NAT.

Should IPSec passthrough be on or off?

It should be on, particularly for corporate VPNs.

Do you need passthrough for VPN?

No, most VPNs don’t require it.