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claude-home/networking/examples/troubleshooting.md
Cal Corum 10c9e0d854 CLAUDE: Migrate to technology-first documentation architecture 
Complete restructure from patterns/examples/reference to technology-focused directories:

• Created technology-specific directories with comprehensive documentation:
  - /tdarr/ - Transcoding automation with gaming-aware scheduling
  - /docker/ - Container management with GPU acceleration patterns
  - /vm-management/ - Virtual machine automation and cloud-init
  - /networking/ - SSH infrastructure, reverse proxy, and security
  - /monitoring/ - System health checks and Discord notifications
  - /databases/ - Database patterns and troubleshooting
  - /development/ - Programming language patterns (bash, nodejs, python, vuejs)

• Enhanced CLAUDE.md with intelligent context loading:
  - Technology-first loading rules for automatic context provision
  - Troubleshooting keyword triggers for emergency scenarios
  - Documentation maintenance protocols with automated reminders
  - Context window management for optimal documentation updates

• Preserved valuable content from .claude/tmp/:
  - SSH security improvements and server inventory
  - Tdarr CIFS troubleshooting and Docker iptables solutions
  - Operational scripts with proper technology classification

• Benefits achieved:
  - Self-contained technology directories with complete context
  - Automatic loading of relevant documentation based on keywords
  - Emergency-ready troubleshooting with comprehensive guides
  - Scalable structure for future technology additions
  - Eliminated context bloat through targeted loading

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>
2025-08-12 23:20:15 -05:00

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Network Troubleshooting Reference

Connectivity Issues

Basic connectivity tests

# Test connectivity
ping <target_ip>
ping -c 4 <target_ip>  # Linux (4 packets)

# Test specific port
telnet <target_ip> <port>
nc -zv <target_ip> <port>  # netcat
nmap -p <port> <target_ip>

# DNS resolution
nslookup <hostname>
dig <hostname>
host <hostname>

Network interface debugging

# Show interfaces
ip addr show
ifconfig

# Show routing table
ip route
route -n

# Show network statistics
netstat -i
ss -i

Service Issues

Port and process debugging

# Show listening ports
netstat -tulpn
ss -tulpn
lsof -i :<port>

# Find process using port
fuser <port>/tcp
lsof -i tcp:<port>

# Show all connections
netstat -an
ss -an

Service status

# Systemd services
systemctl status <service>
systemctl is-active <service>
systemctl is-enabled <service>

# Service logs
journalctl -u <service> -f
journalctl -u <service> --since "1 hour ago"

Firewall Debugging

iptables

# List rules
iptables -L -n -v
iptables -t nat -L -n -v

# Check if rule exists
iptables -C INPUT -p tcp --dport 80 -j ACCEPT

# Temporarily disable firewall
systemctl stop iptables  # CentOS/RHEL
ufw disable              # Ubuntu

UFW (Ubuntu)

# Check status
ufw status verbose

# Show rules by number
ufw status numbered

# Check logs
tail -f /var/log/ufw.log

SSL/TLS Issues

Certificate debugging

# Check certificate details
openssl x509 -in certificate.crt -text -noout
openssl s_client -connect <hostname>:443 -servername <hostname>

# Check certificate chain
openssl s_client -connect <hostname>:443 -showcerts

# Test SSL connection
curl -vI https://<hostname>
wget --no-check-certificate -O /dev/null https://<hostname>

Certificate expiration

# Check expiration date
openssl x509 -in certificate.crt -enddate -noout

# Check remote certificate expiration
echo | openssl s_client -servername <hostname> -connect <hostname>:443 2>/dev/null | openssl x509 -noout -dates

DNS Issues

DNS server testing

# Test specific DNS server
nslookup <hostname> <dns_server>
dig @<dns_server> <hostname>

# Flush DNS cache
# Linux (systemd-resolved)
systemctl restart systemd-resolved
# Linux (nscd)
systemctl restart nscd

DNS configuration

# Check DNS settings
cat /etc/resolv.conf
cat /etc/systemd/resolved.conf

# Test DNS resolution order
getent hosts <hostname>

Performance Issues

Bandwidth testing

# iperf3 testing
# Server: iperf3 -s
# Client: iperf3 -c <server_ip>

# wget speed test
wget -O /dev/null http://speedtest.tele2.net/100MB.zip

Network latency

# Continuous ping with timestamps
ping -D <target>

# MTR (better than traceroute)
mtr <target>
mtr --report <target>

Quick Diagnostics

One-liner network check

# Basic network health
ping -c 1 8.8.8.8 && echo "Internet OK" || echo "No Internet"

# Service accessibility
nc -zv localhost 80 && echo "HTTP service running" || echo "HTTP service down"

Network interface stats

# Interface statistics
cat /proc/net/dev
watch -n 1 cat /proc/net/dev