Your question is Troubleshoot VPN or TCP/IP Routing. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
How would you troubleshoot a connectivity issue involving a VPN or complex TCP/IP routing?
Explain the order of checks you would perform, which commands or observability tools you would use, and how you would distinguish a VPN tunnel problem from routing, DNS, firewall, MTU, or application-layer failures. Include how you would validate the fix without changing multiple variables at once.
Scope: answer from a Linux client perspective, while noting where the approach differs for another operating system.