ip addr show dev eth0 - Show interface detailsip link set eth0 promisc on - Enable promiscuous modeip route add 192.168.2.0/24 via 192.168.1.1 - Add static routeip netns add testns - Create network namespaceping -f -c 100 192.168.1.10 - Flood ping (for testing)traceroute -T -p 443 example.com - TCP traceroutemtr --raw example.com - Combined ping/traceroutenetstat -i | grep eth0 - Interface statisticsss -tulnp | grep ':80' - List listening portssystemctl status NetworkManager - Check service statustcip netns to test isolationiptables -A INPUT -m state --state NEW -p tcp --dport 22 -j ACCEPT - Stateful firewallnft add table ip filter - Create nftables tablefirewall-cmd --permanent --add-rich-rule... - Firewalld configurationufw allow from 192.168.0.0/16 to any port 80 - UFW rulesfail2ban-client status sshd - Check failed login attemptsopenssl s_client -connect example.com:443 - SSL/TLS checktcpdump -nn -i any 'port 22 and dst host 192.168.1.5' - SSH traffic capturegetfacl /etc/shadow - File permission analysisiptables -L -n -v --line-numbers - Detailed rule inspectionsystemctl status fail2ban - Security service managementfail2bandig +short SOA example.com - SOA record lookuphost -a example.com @8.8.8.8 - Specify DNS serversystemd-resolve --flush-caches - Clear DNS cacherndc status - Check BIND server statusdig +trace example.com - Full DNS resolution pathnslookup -query=CAA example.com - CAA record checknamed-checkzone example.com db.example.com - Zone file validationcurl -H "Host: example.com" 127.0.0.1 - Test reverse proxydrill -Y dnssec example.com - DNSSEC validationdig +short -x 93.184.216.34 - Reverse lookuptcpdump -i any -w capture.pcap 'port 80' - HTTP traffic capturetc qdisc add dev eth0 root netem loss 1% - Simulate packet lossnetcat -l -p 8080 -k - Simple HTTP servercurl -v http://example.com - Show HTTP headersnmap -sT -p- 192.168.1.5 - Port scanss -m | grep tcp_rst - Check TCP resetsiptraf-ng - Real-time traffic monitoringjournalctl -u NetworkManager - Network logstcpdump -A | grep 'User-Agent' - Filter HTTP User-Agentspython3 -m http.server 8000 - Test server setupnmapWiresharkbash -c 'echo "Hello World"' - One-liner executionwhile read line; do echo $line; done < hosts.txt - File processingcurl -s https://api.ipify.org | grep -q '192' - IP validationexpect -c 'spawn scp file user@host:/dest' - Automated transfersawk '{print $1}' /etc/passwd | sort | uniq -d - Duplicate user checkgrep -r --include="*.log" "ERROR" /var/log/ - Log analysisjq '.[] | .name' json-file.json - JSON parsingcurl -X POST -d '{"key":"value"}' http://api.example.com - API interactionsystemctl restart --no-block sshd - Parallel service restartcrontab -l | { cat; echo "0 * * * * /path/script.sh"; } | crontab - - Schedule jobsip route show table main - Route tablesip rule add from 192.168.1.10 table 100 prio 1000 - Policy routingiptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-ports 8080 - Port forwardingtc qdisc add dev eth0 root handle 1: htb - HTB traffic shapingcurl --interface eth1 http://example.com - Force interface usagesystemctl mask NetworkManager.service - Disable servicejournalctl -u sshd --since "1 hour ago" - Time-based loggingdig +short -t A -4 example.com - Force IPv4 lookupopenssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout key.pem -out cert.pem - Generate SSL certip6tables -A INPUT -p icmpv6 -j ACCEPT - IPv6 firewallBy completing these modules, you'll master: