{"id":10968,"date":"2026-09-29T00:00:57","date_gmt":"2026-09-29T00:00:57","guid":{"rendered":"https:\/\/fastestvpn.com\/resources\/?p=10968"},"modified":"2026-09-29T15:37:21","modified_gmt":"2026-09-29T15:37:21","slug":"what-is-vpn-passthrough","status":"publish","type":"post","link":"https:\/\/fastestvpn.com\/resources\/what-is-vpn-passthrough\/","title":{"rendered":"What is VPN Passthrough? A 2026 Complete Guide","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Have you ever dug into your router settings and spotted “VPN Passthrough” hidden in a security menu? If yes, you\u2019ve probably wondered what it does and whether you should touch it.\u00a0<\/span><\/p>\n

\"What<\/p>\n

Most people ignore it because not everyone understands it, and some prefer not knowing. Some enable it thinking it will make their VPN faster or more secure. However, neither conclusion is accurate.<\/span><\/p>\n

For this purpose, this guide explains what VPN passthrough is, why it exists, whether you need it, and how to configure it properly on your router<\/a>.<\/span><\/p>\n

\n Get FastestVPN <\/i><\/a>\n <\/div>\n<\/span><\/p>\n

What is VPN Passthrough?<\/h2>\n

VPN passthrough is basically a router setting. It lets you allow VPN traffic to pass through the router’s firewall and NAT (Network Address Translation) system without being blocked.\u00a0<\/span><\/p>\n

It doesn’t create a VPN connection, doesn’t encrypt your data, and doesn’t hide your IP address. So, it simply lets VPN traffic from a device on your network reach an external VPN server.<\/span><\/p>\n

For a more non-technical explanation, you can think of it as a security guard. He\u2019s been given orders to let anyone with a VPN badge pass through. So, the guard isn\u2019t providing the VPN; they\u2019re just not standing in its way.<\/span><\/p>\n

Why Does VPN Passthrough Exist?<\/h2>\n

If you\u2019re still confused about why passthrough is needed, you first need to understand what NAT does. Let\u2019s dive in:\u00a0<\/span><\/p>\n

The NAT Problem<\/h3>\n

Your home router uses NAT to let multiple devices share a single public IP address. So, when your laptop sends a request to the internet, the router swaps your device’s private IP. It exchanges it with a public one, sends the request out, and then routes the response back to your laptop.<\/span><\/p>\n

To do this, NAT relies on port numbers. Every outgoing request gets tagged with a port number. This way, the router knows which device the response belongs to when it comes back.<\/span><\/p>\n

So, what\u2019s the issue here?\u00a0<\/span><\/p>\n

Some older VPN protocols don’t use standard port numbers. PPTP, for example, uses GRE (Generic Routing Encapsulation). This doesn\u2019t have port numbers at all. When NAT sees GRE traffic with no port information, it doesn’t know what to do with it. The traffic gets dropped, and your VPN connection fails.<\/span><\/p>\n

VPN passthrough solves this by telling the router how to handle these older protocols.<\/span><\/p>\n

How Each Protocol is Handled<\/h2>\n

\"VPN<\/p>\n\n\n\n\n\n\n
\n

Protocol<\/h3>\n<\/td>\n

\n

The Problem<\/h3>\n<\/td>\n

\n

Passthrough Solution<\/h3>\n<\/td>\n<\/tr>\n

PPTP<\/b><\/td>\nUses GRE, which has no port numbers.<\/span><\/td>\nEnhanced GRE includes a Call ID that acts like a port number.<\/span><\/td>\n<\/tr>\n
L2TP<\/b><\/td>\nUses UDP but needs special handling.<\/span><\/td>\nSession ID substitutes for a port number.<\/span><\/td>\n<\/tr>\n
IPsec<\/b><\/td>\nUses protocols NAT doesn’t recognize.<\/span><\/td>\nNAT-T wraps IPsec packets inside standard UDP packets.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Types of VPN Passthrough<\/h2>\n

Most routers that support VPN passthrough offer three separate toggles. These include:\u00a0<\/span><\/p>\n

PPTP Passthrough<\/h3>\n

PPTP, or Point-to-Point Tunneling Protocol, is one of the oldest VPN protocols. It uses GRE to encapsulate data, which NAT struggles with.\u00a0<\/span><\/p>\n

PPTP passthrough modifies GRE to include a Call ID that functions like a port number. This allows NAT to route the traffic correctly.<\/span><\/p>\n

TECHNICAL WARNING<\/b>: <\/span>PPTP is considered obsolete and insecure. It uses weak encryption (MS-CHAP v2) that can be cracked. If you’re still using PPTP, you should switch to a modern protocol<\/span><\/i>.<\/span><\/p><\/blockquote>\n

L2TP Passthrough<\/h3>\n

Next is L2TP Passthrough, which is often paired with IPsec for encryption. It uses a Session ID that acts as a substitute for a port number, allowing NAT to track the connection. L2TP passthrough enables this handling.<\/span><\/p>\n

SECURITY NOTE:<\/b> L2TP\/IPsec is more secure than PPTP but is slower and less efficient than modern alternatives like WireGuard or OpenVPN<\/span><\/i>.<\/span><\/p><\/blockquote>\n

IPsec Passthrough<\/h3>\n

IPsec (Internet Protocol Security) is a suite of protocols used to secure internet communications. It doesn’t natively work with NAT because it encrypts the packet headers that NAT needs to read.<\/span><\/p>\n

IPsec passthrough solves this using NAT-T, or NAT Traversal. This means it wraps IPsec packets inside standard UDP packets. NAT can read the UDP header, assign a port number, and route the traffic correctly.<\/span><\/p>\n

PLEASE NOTE<\/b>: <\/span>IPsec is still widely used in corporate VPNs and is considered secure when configured properly<\/span><\/i>.<\/span><\/p><\/blockquote>\n

Do You Actually Need VPN Passthrough?<\/h2>\n

No, you don\u2019t actually need it, and here are a few reasons why:\u00a0<\/span><\/p>\n