Direct answer

When travelling and diagnosing or configuring a VPN connection, the main idea is that a VPN client on your device establishes a connection to a VPN server, then “tunnels” your traffic through that server. What changes during travel is your underlying network (Wi‑Fi vs. cellular, hotel captive portals, carrier routing, and local IP/DNS behavior), which can affect whether the VPN connects, how well it routes traffic, and what you see in connectivity tests.

How it works (key concepts)

A VPN connection typically involves three practical layers:

  • Tunnel establishment: Your device negotiates a secure session with the VPN server. If this step fails, you may see connection errors or the VPN may remain disconnected.
  • Traffic routing: Once the tunnel is up, your device routes selected traffic via the VPN. Depending on settings, this can mean “all traffic” or only certain destinations.
  • Name resolution (DNS): Many user-visible issues are really DNS issues. Even if the tunnel is connected, domain lookups may fail or use the wrong DNS path if DNS routing is not configured as expected.

For travelling, these layers interact with changing IP addresses, different networks, and varying captive-portal or firewall behavior, so the same configuration can behave differently in a new location.

Practical context for diagnostics and configuration

Use a structured approach that separates “VPN connectivity” from “application connectivity”:

  • Confirm VPN state: Check that the app/device reports the tunnel as connected (not just “enabled”).
  • Re-test basic connectivity after changes: After switching networks or updating settings, re-check the VPN state before testing websites or apps.
  • Compare behavior with and without VPN: If an issue only happens with the VPN on, it points to tunnel/routing/DNS settings rather than your device being offline.
  • Check DNS and IP indicators: Look for signs that DNS queries and visible IP/network behavior align with your VPN’s intended routing.
  • If problems persist, test across networks: For example, try a different Wi‑Fi or cellular network to see whether the limitation is location/network specific.