Agent skill

network-diagnostics

Diagnose network connectivity issues: DNS, routing, firewall, port checks, traceroutes. Use for troubleshooting server-to-server communication or client access problems.

View SKILL.md on GitHub Repository
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Install this agent skill to your Project

npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/development/network-diagnostics

SKILL.md

Network Diagnostics Skill

When to Activate

  • User mentions: connectivity, DNS, ping, traceroute, port, firewall, routing, network unreachable
  • User asks why a server can't reach another server
  • User reports "connection refused" or "timeout" errors

Diagnostic Workflow

Step 1: Identify the Target

powershell
# Extract hostname/IP and port from user's description
$target = "hostname-or-ip"
$port = 443  # or whatever port is relevant

Step 2: Basic Connectivity

powershell
# Quick ping test
Test-Connection -ComputerName $target -Count 4

# DNS resolution
Resolve-DnsName $target -Type A
Resolve-DnsName $target -Type AAAA

Step 3: Port Accessibility

powershell
# TCP port test
Test-NetConnection -ComputerName $target -Port $port -InformationLevel Detailed

# Multiple ports at once
@(22, 80, 443, 3389, 5985) | ForEach-Object {
    Test-NetConnection -ComputerName $target -Port $_ -WarningAction SilentlyContinue |
    Select-Object ComputerName, RemotePort, TcpTestSucceeded
}

Step 4: Route Analysis

powershell
# Trace the path
Test-NetConnection -ComputerName $target -TraceRoute

# Or classic tracert for more detail
tracert -d $target

Step 5: Local Firewall Check

powershell
# Check if Windows Firewall might block
Get-NetFirewallRule | Where-Object {
    $_.Enabled -eq 'True' -and $_.Direction -eq 'Outbound'
} | Select-Object DisplayName, Action -First 20

Common Issues & Solutions

Symptom Likely Cause Check
DNS timeout DNS server unreachable nslookup $target 8.8.8.8
Connection refused Service not running Test-NetConnection -Port
Request timeout Firewall blocking Check both local and remote FW
TTL exceeded Routing loop tracert to find the loop
No route to host Missing route Get-NetRoute -DestinationPrefix 0.0.0.0/0

Output Format

Always report:

  1. What was tested
  2. What succeeded ✅
  3. What failed ❌
  4. Recommended next step

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