Here’s a deep dive into advanced Linux networking commands, tools, and techniques — ideal for sysadmins, devops, or security enthusiasts:
🧠 Advanced Linux Networking Commands
🔍 1. Interface & IP Configuration
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ip(replacesifconfig)
ip a # Show IP addresses
ip link set eth0 up # Bring interface up
ip addr add 192.168.1.100/24 dev eth0
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ethtool– View/set Ethernet device parameters
ethtool eth0
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nmcli(NetworkManager CLI)
nmcli con show
nmcli device status
🌐 2. Network Diagnostics
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ping,traceroute
ping -c 4 google.com
traceroute example.com
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mtr(combines ping + traceroute)
mtr google.com
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dig/nslookup– DNS lookups
dig +short mx gmail.com
nslookup google.com
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host
host github.com
🛰️ 3. Socket & Port Inspection
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ss(modern replacement fornetstat)
ss -tuln # TCP/UDP listening ports
ss -s # Summary of connections
ss -p # Show PID of connected processes
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lsof -i
lsof -i :443 # Show which process is using port 443
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fuser
fuser -v 80/tcp # Find process using port 80
📡 4. Scanning & Discovery
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nmap– Network scanner
nmap -sS -Pn 192.168.1.0/24
nmap -A -T4 example.com
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arp-scan
sudo arp-scan --interface=eth0 --localnet
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tcpdump– Packet sniffer
tcpdump -i eth0 port 80
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wireshark/tshark– Deep packet inspection (GUI/CLI)
🔌 5. Connection Testing
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nc(netcat)
nc -zv example.com 22
nc -lvp 1234 # Listen on port 1234
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telnet
telnet smtp.gmail.com 587
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curl/wget
curl -I https://example.com
wget --spider -S https://example.com
🔐 6. Secure File Transfer & Tunneling
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ssh/scp/rsync
ssh user@host
scp file user@host:/dest/
rsync -avzP file user@host:/dest/
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SSH Tunneling
ssh -L 8080:localhost:80 user@remote-host
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Port forwarding with
socat
socat TCP-LISTEN:1234,fork TCP:example.com:80
🧰 7. Network Configuration Files
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/etc/network/interfaces(Debian-based) -
/etc/sysconfig/network-scripts/(RHEL-based) -
/etc/hosts– Manual hostname mapping -
/etc/resolv.conf– DNS resolver settings -
/etc/nsswitch.conf– Name resolution order
📈 8. Real-Time Monitoring
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iftop/nethogs/bmon
sudo iftop -i eth0
sudo nethogs eth0
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vnstat– Bandwidth usage statistics -
iptraf-ng– Detailed traffic stats per interface
🔄 9. Custom Packet Crafting
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hping3
hping3 -S -p 80 example.com
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ncat– Part of Nmap, like netcat but more powerful -
scapy(Python) – Scriptable packet generation
🛡️ 10. Firewall / NAT / VPN
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iptables/nftables
iptables -L -n -v
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ufw– Simple firewall (Ubuntu)
ufw allow 22/tcp
ufw enable
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ip rule,ip route– Advanced routing -
openvpn,wireguard– VPN tools
