Problem category
Networking
DNS, routing, and connectivity.
- published
Cloudflare Tunnel Is Connected but the Public Hostname Returns 502: Unable to Reach Origin Service
Confirm the tunnel is connected and the visitor sees the tunnel-specific 502 Unable to reach the origin service, then match the exact cloudflared log signature to a stopped origin, a wrong ingress scheme, a wrong ingress port, or an untrusted origin certificate.
- published
Docker Published Port Works Locally but Is Unreachable from the LAN
Compare the working local endpoint with the failing LAN endpoint before investigating publication, application listening context or filtering.
- published
Mosquitto Rejects the MQTT Client Connection
Prove TCP reachability to the broker first, then read the MQTT CONNACK refusal code and match the listener-specific authentication on Mosquitto 2.1.x before changing any broker configuration.
- published
Pi-hole Installed but Clients Get No DNS Response
Separate clients bypassing Pi-hole from Pi-hole answering nothing by checking FTL state, a direct query, the upstream path, port 53 ownership, and the effective client resolver before any upstream or DHCP change.
- published
Proxmox VM Reaches Its Gateway but Cannot Reach the Internet
Separate guest addressing, resolution, bridge/segment evidence, outbound policy and upstream reachability after confirming the intended gateway responds.
- published
Synology Tailscale Connected but NAS Is Unreachable
Separate tailnet connectivity, name resolution, the tailnet access policy, DSM firewall rules, and the exact Synology service port before changing the NAS.
- published
Synology Tailscale Subnet Router: LAN Device Unreachable
NAS access works, but a LAN service behind it does not. Separate subnet advertisement, CIDR, approval, access policy, client routing and target-side evidence.
- published
Tailscale Connection Stuck on DERP Relay
The connection works, but DERP persists during poor performance. Compare both peers and network observations before requesting a scoped network-owner investigation.
- published
WireGuard Handshake Succeeds but Traffic Does Not Pass
Confirm the handshake is recent, separate a universal WireGuard configuration issue (AllowedIPs and routes) from a platform-specific Ubuntu Server gateway forwarding or NAT issue, then apply a bounded configuration or gateway change with console recovery and rollback.