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Roughly 60% of 'the network is broken' tickets trace to issues that aren't actually network-layer problems. DNS misconfiguration, application errors, host firewall blocks, and browser cache are more common than routing failures. A disciplined connectivity troubleshooting workflow that starts at the host and works outward catches the non-network issues early.
Walking this ladder isolates the layer. If ping to the gateway fails, the problem is local (host or Layer 2). If ping to remote subnets fails but the gateway works, it's routing. If IP works but names don't, it's DNS. Every step narrows the problem space.
Gateway works, remote subnet works, internet works. From here, the only remaining issues are DNS, TCP port blocking, or application-specific. That's a big narrowing. If any of those pings failed, the failure point tells you where the problem lives.
Notice the `ttl=` in each ping reply. TTL 64 to the gateway means the gateway is the destination (no hops). TTL 63 to the remote subnet means one hop. TTL 117 from Google means 11 hops (128 - 117, starting from the default 128). The TTL decreasing as you go further away confirms you're actually traversing the path you expect.
Connectivity troubleshooting is a discipline of elimination. Start at the host, walk outward, and stop at the first failure. Every test you run should reduce the search space. If you're not narrowing, you're just running commands — that's not troubleshooting, that's looking busy.
Finish the lesson once you have worked through the material. This awards ★ 30 XP.