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Linux Networking Commands Cheat Sheet with Examples pdf

Table of Contents

Linux Networking Commands Cheat Sheet

A quick reference for essential Linux networking commands to help troubleshoot, configure, and monitor networks efficiently. 🚀

Linux Networking Commands

🌍 Network Configuration Commands

Command Description
ip a Show IP addresses and interfaces (use instead of ifconfig).
ip link show Display all network interfaces.
ip route show Show routing table (default gateway, subnets, routes).
ip addr show Displays IP addresses, similar to ifconfig
ifconfig Display or configure network interfaces (deprecated).
nmcli dev status Show NetworkManager status for all interfaces.

Linux_Networking_Commands_Cheat_Sheet .pdf

📡 Network Connectivity & Testing

Command Description
ping -c 4 google.com Send 4 ICMP packets to check connectivity.
traceroute google.com Show path taken by packets to destination.
mtr google.com Combination of ping and traceroute (real-time).
dig google.com Query DNS records for a domain.
nslookup google.com Get DNS resolution for a domain.
curl -I https://google.com Check website response headers.

🔍 Find Open Ports & Network Services

Command Description
netstat -tulnp Show active ports and services (deprecated).
ss -tulnp Show open ports and listening services (modern alternative).
lsof -i :80 Find process using port 80.
nmap -p 22 192.168.1.1 Scan port 22 (SSH) on a specific device.
nmap -sn 192.168.1.0/24 Scan active devices on a subnet.

📶 Monitor Network Traffic

Command Description
tcpdump -i eth0 port 80 Capture network packets on port 80.
iftop -i eth0 Show bandwidth usage per connection.
nload Display live network bandwidth usage.
bmon Interactive bandwidth monitoring tool.
ip -s link Show interface traffic statistics.

🛠 Firewall Management (iptables & firewalld)

Command Description
iptables -L -n -v List all firewall rules.
iptables -A INPUT -p tcp --dport 22 -j ACCEPT Allow SSH traffic.
iptables -A INPUT -p tcp --dport 80 -j DROP Block HTTP traffic.
firewall-cmd --list-all Show current firewalld settings.
firewall-cmd --add-port=8080/tcp --permanent Open port 8080 permanently.

🔗 Network Interface Management

Command Description
ip link set eth0 up Enable network interface.
ip link set eth0 down Disable network interface.
dhclient eth0 Obtain IP address via DHCP.
ethtool eth0 Display Ethernet settings.

📡 Set Up & Manage Routes

Command Description
ip route add default via 192.168.1.1 Set default gateway.
route -n Show routing table (deprecated).
ip route del default Remove default route.

🚀 Advanced Networking Commands

Command Description
tc qdisc add dev eth0 root netem delay 100ms Simulate network latency.
tc qdisc del dev eth0 root Remove latency settings.
curl ifconfig.me Get public IP address.
wget http://speedtest.tele2.net/1MB.zip Download a test file to check network speed.

🔎 Scan & Detect Network Issues

Command Description
arp -a Show ARP table (MAC addresses of connected devices).
whois google.com Get domain registration details.
hostname -I Get local machine IP address.
systemctl restart networking Restart networking service.

These Linux networking commands will help you troubleshoot, monitor, and configure networks efficiently. 🚀

📝 1. Check Network Configuration

📌 Command: ip a – Show IP addresses and interfaces

bash
ip a

🔹 Example Output:

sql
2: eth0: <UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.10/24 brd 192.168.1.255 scope global eth0

✅ Shows IP addresses, MAC addresses, and interface statuses.

🌍 2. Test Network Connectivity

📌 Command: ping – Check if a host is reachable

bash
ping -c 4 google.com

🔹 Sends 4 packets to check connectivity.
🔹 If packets are lost, there might be network issues.

🚀 3. Check Network Routes

📌 Command: ip route – Show routing table

bash
ip route

🔹 Displays default gateway, subnet routes, and interface routes.

📌 Command: traceroute – Show path to a destination

bash
traceroute google.com

🔹 Displays all the hops a packet takes to reach its destination.

📡 4. Scan Open Ports and Listening Services

📌 Command: netstat (Older) or ss (Newer Alternative)

bash
netstat -tulnp # Show active ports and processes
ss -tulnp # Faster alternative to netstat

🔹 t = TCP, u = UDP, l = Listening, n = Numeric, p = Process

🔹 Example Output:

nginx
tcp LISTEN 0 50 0.0.0.0:22 0.0.0.0:* users:(("sshd",pid=1234,fd=3))

✅ This means SSH is listening on port 22.

🔍 5. Find Network Interfaces and Traffic Stats

📌 Command: ip -s link – Show interface statistics

bash
ip -s link

✅ Displays sent/received packets and errors.

📌 Command: ifconfig (Deprecated)

bash
ifconfig eth0

✅ Shows interface details (IP, MAC, status).
(Use ip a instead in modern Linux systems.)

🌍 6. Test DNS Resolution

📌 Command: nslookup – Find IP of a domain

bash
nslookup google.com

✅ Shows Google’s IP addresses from your DNS server.

📌 Command: dig – Detailed DNS lookup

bash
dig google.com

✅ Provides detailed DNS resolution info.

📶 7. Monitor Network Traffic

📌 Command: tcpdump – Capture network packets

bash
tcpdump -i eth0 port 80

✅ Captures HTTP traffic on eth0 interface.

📌 Command: iftop – Monitor bandwidth usage

bash
sudo iftop -i eth0

✅ Shows live network bandwidth usage per connection.

🛠️ 8. Manage Firewall Rules

📌 Command: iptables – Configure firewall rules

✅ Block incoming traffic on port 80:

bash
iptables -A INPUT -p tcp --dport 80 -j DROP

✅ Allow SSH (port 22) traffic:

bash
iptables -A INPUT -p tcp --dport 22 -j ACCEPT

✅ List all rules:

bash
iptables -L -n -v

🔎 9. Scan Network for Active Devices

📌 Command: nmap – Scan devices and open ports

bash
nmap -sn 192.168.1.0/24 # Ping scan for active devices
nmap -p 22 192.168.1.1 # Scan SSH port on a specific device

✅ Helps identify online devices and security vulnerabilities.

🚀 10. Test and Manage Network Speed

📌 Command: speedtest-cli – Check internet speed

bash
speedtest-cli

✅ Shows upload/download speed.

📌 Command: tc – Simulate network latency

✅ Add 100ms delay to all outgoing packets:

bash
tc qdisc add dev eth0 root netem delay 100ms

✅ Remove delay:

bash
tc qdisc del dev eth0 root netem

🚀 BONUS: Advanced Linux Networking Commands

🔄 Restart Network Services

bash
systemctl restart networking

✅ Restart the network service after changes.

🌐 Find Public IP Address

bash
curl ifconfig.me

✅ Displays your external IP address.

📡 Find Default Gateway

bash
ip route | grep default

✅ Shows your default gateway (router IP).

ifconfig replacement command is IP

  • The ip command is more powerful and flexible than ifconfig, and it’s designed to work with the newer Linux networking stack.
  • Alternatives to ifconfig for specific tasks:
    • To display IP addresses: ip addr show.
    • To bring an interface up: ip link set <interface> up.
    • To bring an interface down: ip link set <interface> down.
  • Examples of ip commands:
    • ip addr: Displays IP addresses, similar to ifconfig.
    • ip link: Manages network interfaces (e.g., bring up/down, change MTU).
    • ip route: Manages routing tables.
    • ip tunnel: Configures IP tunnels.