A network issue is easier to narrow down when each test answers a specific question. Inspect local configuration first, then routing, name resolution, and finally the application endpoint.
1. Verify the interface and address
Confirm that the expected interface is up and has an address from the correct subnet. Compare the output with the intended VirtualBox adapter configuration or network plan.
ip -br address ip route
2. Test reachability carefully
A ping to the configured gateway can help test local network reachability. Some systems or networks filter ICMP, so a failed ping alone does not prove that every service is unreachable.
ping -c 4 <gateway-ip> ip neigh
3. Check DNS separately
Test name resolution separately from raw IP connectivity. If an IP endpoint responds but a hostname does not resolve, inspect the resolver configuration and the result from the DNS lookup tool available on that system.
getent hosts example.com resolvectl status
4. Verify the application endpoint
Once address, route, and DNS checks are understood, test the actual destination port or HTTP endpoint. Note the exact error and timeout; these details help distinguish resolution, connection, and application-layer failures.
curl -I --max-time 5 https://example.com ss -lnt