Advanced Linux Networking Commands

 Here’s a deep dive into advanced Linux networking commands, tools, and techniques — ideal for sysadmins, devops, or security enthusiasts:

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🧠 Advanced Linux Networking Commands

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🔍 1. Interface & IP Configuration

• ip (replaces ifconfig)

ip a                # Show IP addresses
ip link set eth0 up # Bring interface up
ip addr add 192.168.1.100/24 dev eth0

• ethtool – View/set Ethernet device parameters

ethtool eth0

• nmcli (NetworkManager CLI)

nmcli con show
nmcli device status

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🌐 2. Network Diagnostics

• ping, traceroute

ping -c 4 google.com
traceroute example.com

• mtr (combines ping + traceroute)

mtr google.com

• dig / nslookup – DNS lookups

dig +short mx gmail.com
nslookup google.com

• host

host github.com

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🛰️ 3. Socket & Port Inspection

• ss (modern replacement for netstat)

ss -tuln               # TCP/UDP listening ports
ss -s                  # Summary of connections
ss -p                  # Show PID of connected processes

• lsof -i

lsof -i :443           # Show which process is using port 443

• fuser

fuser -v 80/tcp        # Find process using port 80

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📡 4. Scanning & Discovery

• nmap – Network scanner

nmap -sS -Pn 192.168.1.0/24
nmap -A -T4 example.com

• arp-scan

sudo arp-scan --interface=eth0 --localnet

• tcpdump – Packet sniffer

tcpdump -i eth0 port 80

• wireshark / tshark – Deep packet inspection (GUI/CLI)

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🔌 5. Connection Testing

• nc (netcat)

nc -zv example.com 22
nc -lvp 1234           # Listen on port 1234

• telnet

telnet smtp.gmail.com 587

• curl / wget

curl -I https://example.com
wget --spider -S https://example.com

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🔐 6. Secure File Transfer & Tunneling

• ssh / scp / rsync

ssh user@host
scp file user@host:/dest/
rsync -avzP file user@host:/dest/

• SSH Tunneling

ssh -L 8080:localhost:80 user@remote-host

• Port forwarding with socat

socat TCP-LISTEN:1234,fork TCP:example.com:80

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🧰 7. Network Configuration Files

• /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

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📈 8. Real-Time Monitoring

• iftop / nethogs / bmon

sudo iftop -i eth0
sudo nethogs eth0

• vnstat – Bandwidth usage statistics

• iptraf-ng – Detailed traffic stats per interface

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🔄 9. Custom Packet Crafting

• hping3

hping3 -S -p 80 example.com

• ncat – Part of Nmap, like netcat but more powerful

• scapy (Python) – Scriptable packet generation

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🛡️ 10. Firewall / NAT / VPN

• iptables / nftables

iptables -L -n -v

• ufw – Simple firewall (Ubuntu)

ufw allow 22/tcp
ufw enable

• ip rule, ip route – Advanced routing

• openvpn, wireguard – VPN tools

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