# Linux Networking Commands ## ip Command - Interface and Address Management The ip command is the primary tool for network configuration on modern Linux systems. ip addr show - displays all network interfaces with their IP addresses ip addr show eth0 - shows only the eth0 interface ip addr add 192.168.1.100/24 dev eth0 - adds an IP address to an interface ip addr del 192.168.1.100/24 dev eth0 - removes an IP address from an interface ip link show - shows link layer information for all interfaces ip link set eth0 up - brings an interface up ip link set eth0 down - brings an interface down ## ip Command - Routing ip route show - displays the routing table ip route add 192.168.2.0/24 via 192.168.1.1 - adds a static route ip route del 192.168.2.0/24 - removes a route ip route add default via 192.168.1.254 - adds a default gateway ## ping Command ping 192.168.1.1 - pings an IP address continuously ping -c 4 192.168.1.1 - sends exactly 4 ping packets ping -i 2 192.168.1.1 - sends pings every 2 seconds ping -s 1400 192.168.1.1 - sends pings with 1400 byte payload ping6 2001:db8::1 - pings an IPv6 address ## traceroute Command traceroute 8.8.8.8 - traces the route to Google DNS traceroute -n 8.8.8.8 - does not resolve hostnames, faster output traceroute -T 8.8.8.8 - uses TCP instead of UDP for probes ## netstat and ss Commands netstat -tlnp - shows listening TCP ports with process names netstat -tulnp - shows listening TCP and UDP ports ss -tlnp - modern replacement for netstat shows listening TCP ports ss -s - shows summary statistics ss -o state established - shows established connections ## nslookup and dig Commands nslookup google.com - resolves a domain name nslookup -type=mx gmail.com - looks up mail exchange records dig google.com - detailed DNS lookup dig google.com A - looks up A record specifically dig @8.8.8.8 google.com - queries a specific DNS server dig google.com +short - returns only the IP address ## tcpdump Command tcpdump -i eth0 - captures all packets on eth0 tcpdump -i eth0 host 192.168.1.1 - captures packets to or from that host tcpdump -i eth0 port 80 - captures HTTP traffic tcpdump -i eth0 -w capture.pcap - saves packets to a file tcpdump -r capture.pcap - reads and displays saved capture file tcpdump -i eth0 tcp and port 443 - captures HTTPS traffic ## arp Command arp -a - shows the ARP cache arp -d 192.168.1.1 - deletes an ARP entry arp -s 192.168.1.1 aa:bb:cc:dd:ee:ff - adds a static ARP entry ## Other Useful Commands hostname - shows the computer hostname ifconfig - older interface configuration command curl -I https://example.com - fetches HTTP headers only wget https://example.com/file - downloads a file nc -zv 192.168.1.1 80 - tests if port 80 is open on a host nmap 192.168.1.0/24 - scans a network for live hosts and open ports