network-diagnostics

name	network-diagnostics
description	Diagnose network connectivity issues: DNS, routing, firewall, port checks, traceroutes. Use for troubleshooting server-to-server communication or client access problems. Use when this capability is needed.

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

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

Step 2: Basic Connectivity

# 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

# 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

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

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

Step 5: Local Firewall Check

# 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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