net-ops
Network Operations
Diagnose network problems on Windows, macOS, or Linux with a layered ladder that isolates faults to the smallest possible scope, then pattern-match against OS-specific culprits. Designed for the common case: someone reports "internet broken" on a box you can shell into (locally or via SSH).
The Universal Insight
Bypass-tool succeeds while OS-resolver fails is a smoking gun on every platform. It means DNS infrastructure is healthy but the operating system's name-resolution path is hooked or misconfigured. The bypass tool differs per OS but the discriminator is identical:
| OS | Bypass tool | OS resolver tool | If bypass works but resolver fails |
|---|---|---|---|
| Windows | nslookup |
Resolve-DnsName, browsers |
NRPT, WFP, HOSTS, LSP, local 127.0.0.1:53 proxy |
| macOS | dig @1.1.1.1 |
dscacheutil -q host, browsers |
/etc/resolver/*, scutil DNS, profiles, mDNSResponder, kext |
| Linux | dig @1.1.1.1 |
getent hosts, resolvectl query |
systemd-resolved, /etc/resolv.conf, NetworkManager, dnsmasq, NSS |
The bypass tool implements its own resolver and talks straight to UDP/53. The OS resolver tool goes through the full system name-service path including all hooks. Comparing the two narrows the suspect list dramatically.
The Diagnostic Ladder
Walk down the layers in order. Do not skip rungs. Each rung has a binary outcome that eliminates everything above it. Per-OS tools are in references/diagnostic-ladder.md; the structure is universal.