network

name	network
category	web
description	Network diagnostics, DNS lookup, port scanning, and connectivity testing. Use when the user asks to check if a host is reachable, trace network routes, resolve DNS records, inspect open ports, debug HTTP requests, check SSL/TLS certificates, test bandwidth, diagnose network latency, or troubleshoot connectivity issues using ping, traceroute, dig, nslookup, netstat, ss, curl, and related tools.
license	MIT
compatibility	Requires standard networking tools (ping, curl, dig). Some tools may need installation on minimal systems
metadata	{"author":"zeph","version":"1.0"}

Network Diagnostics

Before running commands, detect the OS and load the matching reference for platform-specific syntax:

• Linux — references/linux.md (ss, ip, iptables/nftables, iproute2)
• macOS — references/macos.md (lsof, ifconfig, pfctl, networkQuality)
• Windows — references/windows.md (PowerShell: Test-NetConnection, Get-NetTCPConnection)

OS detection:

uname -s 2>/dev/null || echo Windows

Quick Reference

Task	Command
Check host reachability	ping -c 4 host
Trace route to host	traceroute host
DNS lookup	dig +short host
Reverse DNS	dig -x IP
Check specific port	nc -zv host port
HTTP status	curl -sI -o /dev/null -w "%{http_code}" URL
SSL certificate	openssl s_client -connect host:443 </dev/null

Diagnostic Workflow

Is a service accessible?

1. DNS resolves — dig +short host
2. Host reachable — ping -c 2 host
3. Port open — nc -zv -w 3 host 443
4. HTTP responds — curl -sI -o /dev/null -w "%{http_code}" https://host
5. SSL valid — openssl s_client -connect host:443 </dev/null 2>/dev/null | openssl x509 -noout -checkend 0

Diagnose slow connections

1. DNS time — dig +stats host | grep "Query time"
2. Latency — ping -c 10 host
3. Route bottleneck — mtr -r -c 10 host (or traceroute host)
4. HTTP timing — use curl timing breakdown (see below)

HTTP Debugging (curl, cross-platform)

# Response headers
curl -sI https://host

# Status code only
curl -s -o /dev/null -w "%{http_code}" https://host

# Full verbose debug
curl -v https://host 2>&1

# Follow redirects
curl -sIL https://host

# Timing breakdown
curl -s -o /dev/null -w "\
  DNS:     %{time_namelookup}s\n\
  Connect: %{time_connect}s\n\
  TLS:     %{time_appconnect}s\n\
  TTFB:    %{time_starttransfer}s\n\
  Total:   %{time_total}s\n\
  Status:  %{http_code}\n\
  Size:    %{size_download} bytes\n" https://host

# Resolve to specific IP (bypass DNS)
curl --resolve host:443:93.184.216.34 https://host

# Test specific Host header
curl -s -H "Host: host" http://10.0.0.1/

SSL/TLS Inspection (cross-platform)

# Certificate details
openssl s_client -connect host:443 </dev/null 2>/dev/null | \
  openssl x509 -noout -subject -issuer -dates

# Expiration check
openssl s_client -connect host:443 </dev/null 2>/dev/null | \
  openssl x509 -noout -enddate

# Full certificate chain
openssl s_client -connect host:443 -showcerts </dev/null

# TLS version check
openssl s_client -connect host:443 -tls1_2 </dev/null 2>&1 | head -5
openssl s_client -connect host:443 -tls1_3 </dev/null 2>&1 | head -5

# Quick SSL check via curl
curl -vI https://host 2>&1 | grep -E '^\*'

DNS Concepts

Record	Purpose
A / AAAA	IPv4 / IPv6 address
MX	Mail exchange server
NS	Authoritative name server
TXT	SPF, DKIM, DMARC, verification
CNAME	Alias to another domain
SOA	Zone authority info
SRV	Service location (port + host)
CAA	Certificate authority authorization
PTR	Reverse DNS (IP → hostname)

Important Notes

• ping uses ICMP — some hosts block it; a failed ping does not mean the host is down
• traceroute uses UDP on Linux, ICMP on macOS — use OS-specific reference for flags
• dig is preferred over nslookup for scripting (predictable output)
• Port/socket tools differ by OS: Linux uses ss, macOS uses lsof, Windows uses Get-NetTCPConnection
• Always use timeouts (-W, -w, --connect-timeout) in scripts
• Running network scans against systems you do not own may violate terms of service