VPNs Explained: How the Encrypted Tunnel Works — and Its Real Pros & Cons

A Virtual Private Network (VPN) creates a secure, encrypted tunnel between your device and a server somewhere else on the internet. Everything you send and receive travels inside that tunnel, hidden from anyone sitting between you and the VPN server. In this post I break down exactly how that works and give you an honest view of the trade-offs.

What a VPN actually does to your traffic

When you connect without a VPN, your traffic hops from your device to your router, to your ISP, and out across the public internet. Anyone along that path — the coffee-shop Wi-Fi owner, your ISP, a network attacker — can potentially see where you are going and, for unencrypted sites, what you are doing.

A VPN changes the picture in three ways:

• Encryption — Your data is scrambled before it leaves your device, so intermediaries see only ciphertext.
• Tunneling — Your real packets are wrapped inside new packets addressed to the VPN server. This is called encapsulation.
• IP masking — Websites see the VPN server's IP address instead of yours.

The tunnel, step by step

1. Authentication — Your client proves its identity to the VPN server (certificate, key, or credentials).
2. Key exchange — Both sides agree on encryption keys using a handshake such as the one in WireGuard or IKEv2/IPsec.
3. Encapsulation — Each outgoing packet is encrypted and placed inside an outer packet destined for the VPN server.
4. Decryption & forwarding — The server unwraps the packet, decrypts it, and forwards it to the real destination on your behalf.
5. Return trip — Responses come back to the server, get encrypted, and are tunneled back to you.

Common VPN protocols

• WireGuard — Modern, fast, small codebase. My default choice for new deployments.
• OpenVPN — Battle-tested and highly configurable, but heavier.
• IKEv2/IPsec — Great for mobile because it reconnects quickly when you switch networks.

A VPN moves your point of trust. You are no longer trusting the coffee-shop Wi-Fi — you are trusting your VPN provider instead. Choose that provider carefully.

The Pros

• Privacy on untrusted networks — Public Wi-Fi becomes far safer.
• Hides your IP — Useful for reducing tracking and geolocation.
• Bypasses local restrictions — Access resources as if you were in another location.
• Secures remote work — Employees can reach internal systems safely.

The Cons

• You must trust the provider — They can technically see your traffic as it exits the tunnel.
• Speed can drop — Encryption overhead and distant servers add latency.
• Not full anonymity — Logins, cookies, and browser fingerprinting still identify you.
• Some services block VPNs — Streaming and banking sites often reject known VPN IPs.
• A false sense of security — A VPN does not stop malware, phishing, or a compromised device.

When a VPN is the right tool

Use one when you are on networks you do not control, when you need to reach a private network remotely, or when you want to reduce casual tracking. Do not treat it as a magic privacy shield — it is one layer in a larger defense, not the whole wall.