Why Caddy Gives 502 When the Backend Works Fine by IP
A 502 usually means the browser-to-Caddy leg worked and the Caddy-to-upstream leg did not.
troubleshooting
Local DNS Failure Can Look Like a Dead Server
Test the known address before rebooting a host just because its name stopped resolving.
Dashboards Should Follow Troubleshooting Workflows
A wall of attractive graphs is slow during an incident if related signals are scattered by exporter rather than by the question an operator is trying to answer.
Why I Started Saving Packet Captures with the Incident Notes
A short pcap plus context is often more useful six months later than a page of remembered conclusions.
Network Reliability Starts by Naming the Failure Domain
Resolve the symptom into DNS, routing, transport, policy, ingress or application before changing configuration.
Using `dig` to Stop Treating DNS Like a Black Box
`dig` gave me a way to separate resolver configuration, authoritative answers, record types and response timing instead of reducing DNS to 'name works' or 'name fails'.
Caddy Logs Exist, but They Still Do Not Answer Which User Request Failed
Logs become useful when access records, proxy errors and request identity can be correlated.
Ping Works but the Browser Does Not: Separating IP, DNS and Applications
Connectivity tests become useful only when each test is tied to a layer: local addressing, routing, DNS resolution, TCP reachability and the application itself.
A Year of Small Network Labs: What Broke Most Often
Most beginner lab failures were not exotic protocol bugs. They were wrong masks, wrong VLANs, missing routes, stale assumptions and tests that did not isolate the failing layer.
My Tailscale Failure Drill for a Home Server: Name, Peer, Policy, Port, Service
I troubleshoot from the network boundary inward so I do not restart a healthy server because one naming or authorization layer failed.
SIP Ladder Diagrams Became More Useful When I Added Media Events
A signalling-only ladder can say a call succeeded while the user heard silence; adding SDP and RTP events fixes that blind spot.
The ACL That Worked Perfectly and Locked Me Out
My first memorable ACL mistake was technically correct: it blocked exactly what I told it to block, including the management traffic I still needed.
When One VLAN Would Not Cross the Trunk
A trunk can be up while one VLAN is still broken. That lab pushed me to verify allowed VLANs and operational state instead of assuming the link was simply good or bad.
SIP and 5G Core Troubleshooting Started Converging for Me
Different protocols, same debugging discipline: establish state, identify the boundary, then follow the next dependency.
sngrep Became the Fastest Way to Answer the First SIP Question
Before opening a full packet capture, sngrep gave me a quick view of call legs, response codes and dialog timing directly on the server.
Backup Journals Make Failed Automation Debuggable
A red backup alert identifies the outcome but usually does not explain which command, mount or permission caused the failure.
tcpdump Became My First Tool Before Wireshark
On a headless Linux box, tcpdump was faster than moving captures around blindly. A narrow capture at the right interface often answered the question immediately.
The Call Connected but Only One Side Had Audio
One-way audio was my first VoIP problem where the signaling looked healthy and the real fault was the address and port information used for RTP.