netscrew.dev/commands/check
Command

n check

Diagnostic triage ladder or target health check

Short forms:c · ch · chk · health · diag · diagnostics · triage

Usage — n check

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  Netscrew ("n") — check (c, ch, chk) — Diagnose a host (reachability, latency, MAC, ports, web) or the local network ladder
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USAGE:
  n c .                                4-stage connectivity ladder for THIS machine (loopback→gateway→WAN→DNS)
  n c <host>                           full triage of a host: ping, resolve, MAC/vendor, ports, HTTP/TLS

OPTIONS:
  --probe                          also port/web-probe PUBLIC hosts (LAN/VPN are always probed)

Target: . = this machine · <host> = remote
Deeper: n c -h = the concept/theory behind this command  ·  n -h ports  ·  n -h rtt

The concept behind it — n check -h

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  NETSCREW GUIDE: Network Connectivity Triage Ladder ("n check" / "n health")
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OVERVIEW:
  During a network outage or connectivity failure, running individual pings and
  inspecting routes by hand wastes critical minutes. n health automates the
  classic 4-stage network triage ladder in 2 seconds.

THE 4-STAGE TRIAGE LADDER:
  1. Loopback Stack (127.0.0.1)
     Verifies the kernel network subsystem and localhost interface are alive.
     Failure means: Kernel network stack panic or 'lo' interface is down.

  2. Default Gateway & LAN (ip route -> router IP)
     Finds your default gateway IP and pings it via the primary network interface.
     Failure means: Physical Ethernet cable disconnected, WiFi down, or switch fault.

  3. Outbound WAN Internet (1.1.1.1 / 8.8.8.8)
     Pings public anycast DNS root IPs to verify traffic leaves your local LAN.
     Failure means: Gateway/modem is up, but ISP uplink or external routing has dropped.

  4. DNS Name Resolution (google.com)
     Tests resolving a public domain name using the local nameserver configuration.
     Failure means: Internet is reachable, but DNS servers in /etc/resolv.conf are dead.

TARGET HOST & DEVICE DIAGNOSTIC TRIAGE:
  Pass any IP address or domain name to run an instant deep diagnostic triage:
  • n health 192.168.1.119   (Ping latency, Layer 2 MAC, OUI vendor, open management ports)
  • n health github.com       (DNS lookup time, TTL hops, HTTP headers & SSL cert expiry)

USAGE:
  n check                  Run local 4-stage connectivity triage ladder
  n check <IP | DOMAIN>    Run comprehensive target host diagnostic triage
  n check -h               Show this guide page (alias: "n health")