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CBT Nuggets

Networking · Intermediate

VPN (Virtual Private Network)

A VPN extends a private network across an untrusted network like the public internet by encrypting traffic between two endpoints and authenticating both sides of the tunnel.

For IT leaders

VPN is still a default building block for hybrid cloud, partner connectivity, and remote access; a team that cannot debug it owns its outages.

Why IT teams care

Where this shows up at the team level

  • Hybrid-cloud, branch-to-headquarters, and partner integrations all rely on site-to-site VPN.
  • Remote-access VPN remains a primary path for vendors, contractors, and emergency access even alongside zero-trust tools.
  • VPN failures often correlate with tunnel timeouts, NAT changes, or certificate rotations that need clear ownership.

In production

Where teams encounter it

  • Site-to-site IPsec VPNs between offices and to AWS / Azure / Google Cloud
  • Remote-access SSL or IKEv2 VPNs for employees and contractors
  • Branch SD-WAN devices terminating VPN overlays

How it works

How VPN actually works

  1. 01VPN endpoints negotiate keys (commonly via IKE) and then encrypt and encapsulate IP traffic in IPsec or SSL/TLS for transport across the untrusted network.
  2. 02Site-to-site VPNs connect two networks transparently to users; remote-access VPNs connect a single device into a network.
  3. 03Modern designs combine VPN with identity, posture, and zero-trust policy so access does not depend on tunnel-only trust.
  4. 04Performance and reliability depend on encryption choices, MTU/MSS settings, and the underlying internet path.

In practice

Common team use cases

  • Connecting branch offices to headquarters or to cloud landing zones
  • Giving remote employees and vendors secure access to internal apps
  • Extending on-prem networks into cloud VPCs without dedicated circuits

Build the capability

Each link routes to a hub that goes deeper than this definition.

Related concepts

Close the team gap

Turn this concept into team capability

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