Essential Linux Networking Commands Every Admin Must Know (2026)

Networking is the backbone of modern IT infrastructure. Whether you're managing web servers, troubleshooting connectivity issues, or configuring firewall rules, you need a solid command of Linux networking tools. This guide covers every essential networking command you'll use as a Linux administrator, with practical, real-world examples.

Interface Configuration with ip

The ip command has replaced the legacy ifconfig and is the standard tool for network interface management on modern Linux distributions.

Viewing Network Interfaces

# Show all interfaces with IP addresses
ip addr show
ip a

# Show specific interface
ip addr show eth0

# Show only IPv4 addresses
ip -4 addr show

# Show brief interface summary
ip -br addr show
# Output: eth0  UP  192.168.1.100/24
#         lo    UP  127.0.0.1/8

Managing IP Addresses

# Add an IP address
sudo ip addr add 192.168.1.200/24 dev eth0

# Remove an IP address
sudo ip addr del 192.168.1.200/24 dev eth0

# Bring interface up/down
sudo ip link set eth0 up
sudo ip link set eth0 down

Routing Table Management

# Show routing table
ip route show
ip r

# Add a static route
sudo ip route add 10.0.0.0/8 via 192.168.1.1

# Add default gateway
sudo ip route add default via 192.168.1.1

# Delete a route
sudo ip route del 10.0.0.0/8

Connection Analysis with ss

The ss (socket statistics) command is the modern replacement for netstat, offering faster performance and more detailed output:

# List all TCP connections
ss -t

# List all listening ports
ss -tlnp

# List all UDP sockets
ss -ulnp

# Show connections with process info
ss -tulnp

# Filter by port
ss -tlnp sport = :443

# Filter by state
ss state established

# Show connection summary
ss -s

DNS Troubleshooting

dig — DNS Lookup

# Basic DNS lookup
dig example.com

# Query specific record types
dig example.com MX
dig example.com NS
dig example.com TXT
dig example.com AAAA

# Use specific DNS server
dig @8.8.8.8 example.com

# Short output
dig +short example.com

# Trace DNS resolution path
dig +trace example.com

# Reverse DNS lookup
dig -x 93.184.216.34

nslookup and host

# Quick DNS lookup
nslookup example.com
host example.com

# Reverse lookup
host 93.184.216.34

Connectivity Testing

ping — ICMP Echo

# Basic ping
ping example.com

# Limit count
ping -c 5 example.com

# Set interval (seconds)
ping -i 0.5 -c 10 example.com

# Set packet size
ping -s 1472 example.com

# IPv6 ping
ping6 example.com

traceroute — Path Tracing

# TCP traceroute (more reliable through firewalls)
traceroute -T example.com

# UDP traceroute (default)
traceroute example.com

# ICMP traceroute
traceroute -I example.com

# mtr — combines ping and traceroute
mtr example.com
mtr --report -c 10 example.com

Packet Capture with tcpdump

The tcpdump command is indispensable for deep network troubleshooting:

# Capture on specific interface
sudo tcpdump -i eth0

# Capture specific number of packets
sudo tcpdump -i eth0 -c 100

# Filter by host
sudo tcpdump -i eth0 host 192.168.1.50

# Filter by port
sudo tcpdump -i eth0 port 443

# Filter by protocol
sudo tcpdump -i eth0 tcp
sudo tcpdump -i eth0 udp

# Save to file for analysis in Wireshark
sudo tcpdump -i eth0 -w capture.pcap

# Read from capture file
tcpdump -r capture.pcap

# Show packet contents in ASCII
sudo tcpdump -i eth0 -A port 80

# Complex filters
sudo tcpdump -i eth0 'src 192.168.1.0/24 and dst port 443'

Network Scanning with nmap

# Basic port scan
nmap 192.168.1.1

# Scan specific ports
nmap -p 22,80,443 192.168.1.1

# Scan port range
nmap -p 1-1024 192.168.1.1

# Service version detection
nmap -sV 192.168.1.1

# OS detection
sudo nmap -O 192.168.1.1

# Scan entire subnet
nmap 192.168.1.0/24

# Quick scan (top 100 ports)
nmap -F 192.168.1.0/24

# Stealth SYN scan
sudo nmap -sS 192.168.1.1

File Transfer Tools

curl and wget

# Download a file
curl -O https://example.com/file.tar.gz
wget https://example.com/file.tar.gz

# Follow redirects
curl -L https://example.com/redirect

# POST request with data
curl -X POST -d "user=admin&pass=secret" https://api.example.com/login

# Custom headers
curl -H "Authorization: Bearer token123" https://api.example.com/data

# Download with progress bar
curl --progress-bar -O https://example.com/large-file.iso

scp and rsync

# Copy file to remote server
scp file.txt user@server:/remote/path/

# Copy directory recursively
scp -r /local/dir/ user@server:/remote/path/

# Rsync with compression and progress
rsync -avz --progress /local/dir/ user@server:/remote/dir/

# Rsync with SSH on custom port
rsync -avz -e "ssh -p 2222" /local/ user@server:/remote/

Network Configuration Files

Key Configuration Files

# DNS resolver configuration
cat /etc/resolv.conf

# Hostname configuration
cat /etc/hostname
hostnamectl

# Network interfaces (Debian/Ubuntu)
cat /etc/network/interfaces

# Network Manager connections
nmcli connection show

# Hosts file
cat /etc/hosts

Bandwidth and Performance Testing

# iperf3 — bandwidth testing
# Server side
iperf3 -s

# Client side
iperf3 -c server-ip

# Test UDP performance
iperf3 -c server-ip -u -b 100M

# nload — real-time bandwidth monitor
nload eth0

# iftop — per-connection bandwidth
sudo iftop -i eth0

# nethogs — per-process bandwidth
sudo nethogs eth0

Troubleshooting Workflow

When facing network issues, follow this systematic approach:

1. Check interface status: ip link show — Is the interface UP?
2. Check IP configuration: ip addr show — Is an IP assigned?
3. Check routing: ip route show — Is the default gateway set?
4. Check DNS: dig example.com — Can names resolve?
5. Check connectivity: ping gateway-ip → ping 8.8.8.8 → ping example.com
6. Check services: ss -tlnp — Is the service listening?
7. Check firewall: iptables -L -n or nft list ruleset
8. Deep inspection: tcpdump -i eth0 port 80