Troubleshooting Your VPN Connection: Common Issues and Fixes

What to Do When Your VPN Won’t Connect

Setting up a VPN can sometimes be tricky, as network issues can prevent a successful connection. The ‘Ubuntu System Administration Guide’ provides a helpful troubleshooting section for common VPN problems.

Common VPN Hurdles

• Local Firewalls: The most common issue is a firewall on either the client or the server (or somewhere in between) blocking the VPN port. You can use a tool like `telnet` to check if you can establish a basic connection on the required port (e.g., UDP port 1194 for OpenVPN).
• Packet Forwarding: If you can connect to the VPN but can’t access other devices on the remote network, you might have forgotten to enable IP packet forwarding on the VPN server.
• Blocked Ports: Some public networks (like at hotels or airports) block common VPN ports. A common trick is to change your VPN server’s port to a standard, less-likely-to-be-blocked port, such as 443 (the port for HTTPS traffic).

By systematically checking these common points of failure, you can quickly diagnose and fix most VPN connectivity issues.

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This post is based from content of the book Ubuntu System adminstration guide. And the book can be found here https://www.amazon.com/stores/Mattias-Hemmingsson/author/B0FF5CQX13