Table of Contents
- Network Discovery
- Connectivity Testing
- Port Analysis
- Network Performance
- DNS Operations
- VPN Management
- Firewall Operations
- Traffic Analysis
- Security Scanning
Network Discovery
Scan Network Range
# Quick network scan
nmap -sn 192.168.1.0/24
# Detailed host scan
nmap -A 192.168.1.0/24
# List all active IPs
ip neigh show
arp -aInterface Management
# Show interfaces
ip link show
ifconfig -a
# Interface details
ip addr show dev eth0
ethtool eth0
# Monitor interface traffic
iftop -i eth0Connectivity Testing
Basic Connectivity
# Test reachability
ping -c 4 target.com
# Trace route
traceroute target.com
mtr target.com
# Quick port check
nc -zv target.com 80Advanced Testing
# TCP connection test
telnet target.com 80
# SSL connection test
openssl s_client -connect target.com:443
# UDP port test
nc -zuv target.com 53Port Analysis
Port Scanning
# Quick port scan
nmap -F target.com
# Full port scan
nmap -p- target.com
# Service version detection
nmap -sV target.comOpen Port Monitoring
# List listening ports
netstat -tulpn
ss -tulpn
# Check specific port
lsof -i :80Network Performance
Bandwidth Testing
# Server mode
iperf3 -s
# Client mode
iperf3 -c server_ip
# UDP test
iperf3 -u -c server_ip -b 100MConnection Monitoring
# Monitor connections
netstat -ant | grep ESTABLISHED
ss -ant | grep ESTABLISHED
# Connection statistics
netstat -s
ss -sDNS Operations
DNS Queries
# Basic lookup
dig example.com
# Reverse lookup
dig -x IP_ADDRESS
# DNS trace
dig +trace example.com
# All records
dig example.com ANYDNS Troubleshooting
# Check nameservers
dig NS example.com
# Test specific nameserver
dig @8.8.8.8 example.com
# Check MX records
dig MX example.comVPN Management
OpenVPN
# Start OpenVPN server
systemctl start openvpn@server
# Check VPN status
systemctl status openvpn@server
# Client connection
openvpn --config client.ovpnCloudflare WARP
# Connect WARP
warp-cli connect
# Check status
warp-cli status
# Enable Zero Trust
warp-cli teams-enroll <token>Firewall Operations
UFW Management
# Allow service
sudo ufw allow ssh
sudo ufw allow http
# Check status
sudo ufw status verbose
# Enable logging
sudo ufw logging oniptables Rules
# Allow incoming port
sudo iptables -A INPUT -p tcp --dport 80 -j ACCEPT
# Allow established connections
sudo iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
# Save rules
sudo netfilter-persistent saveTraffic Analysis
Packet Capture
# Capture on interface
tcpdump -i eth0
# Capture specific port
tcpdump -i eth0 port 80
# Write to file
tcpdump -i eth0 -w capture.pcapConnection Tracking
# Track connections
netstat -ant
ss -ant
# Monitor real-time
watch -n1 'netstat -ant | grep ESTABLISHED'Security Scanning
Network Security
# Security scan
nmap -sV --script vuln target.com
# Check open ports
nmap -sS target.com
# SSL certificate check
openssl s_client -connect target.com:443Service Testing
# Test web server
curl -Iv https://target.com
# Test mail server
nc -v mail.target.com 25
# Test SSH server
ssh -v [email protected]Quick Solutions for Common Tasks
Website Accessibility
# Full check
curl -Iv https://website.com
nc -zv website.com 443
dig website.comMail Server Issues
# Check mail setup
dig MX domain.com
nc -zv mail.domain.com 25
openssl s_client -connect mail.domain.com:587Network Performance Issues
# Basic tests
ping gateway_ip
mtr problem_host
iperf3 -c test_serverDNS Problems
# Full DNS check
dig +trace domain.com
nslookup domain.com
dig domain.com ANYSecurity Audit
# Basic security check
nmap -sV target.com
sudo ufw status
netstat -tulpnVPN Troubleshooting
# Connection check
ping vpn_gateway
traceroute vpn_gateway
systemctl status openvpnRemember:
- Always check permissions before running commands
- Document changes to network configuration
- Keep logs of troubleshooting steps
- Use appropriate flags for verbosity
- Consider security implications
- Backup configurations before changes
This cheatsheet covers the most common networking tasks. For detailed options and advanced usage, refer to the respective man pages or documentation.