Network Tools

Essential networking utilities for troubleshooting and diagnostics.

Ping

COMMAND	DESCRIPTION
ping host	Ping host
ping -c 4 host	Ping 4 times
ping -i 0.2 host	Ping every 0.2 seconds
ping -s 1500 host	Set packet size to 1500 bytes
ping -f host	Flood ping (root only)

Traceroute

COMMAND	DESCRIPTION
traceroute host	Trace route to host
traceroute -n host	No DNS lookup
traceroute -p 80 host	Use specific port
traceroute -w 1 host	Wait 1 second for response

DNS Tools

nslookup

COMMAND	DESCRIPTION
nslookup host	DNS lookup
nslookup -type=A host	A record lookup
nslookup -type=MX host	MX record lookup
nslookup -type=NS host	NS record lookup
nslookup host 8.8.8.8	Use specific DNS server

dig

COMMAND	DESCRIPTION
dig host	DNS lookup (detailed)
dig +short host	Short output
dig @8.8.8.8 host	Use specific DNS server
dig MX host	MX record lookup
dig NS host	NS record lookup
dig TXT host	TXT record lookup
dig +trace host	Trace DNS lookup

host

COMMAND	DESCRIPTION
host host	DNS lookup
host -t A host	A record lookup
host -t MX host	MX record lookup
host -t NS host	NS record lookup

Curl

Basic Usage

COMMAND	DESCRIPTION
curl URL	GET request
curl -I URL	HEAD request (headers only)
curl -X POST URL	POST request
curl -d "data" URL	POST data
curl -o file URL	Save to file
curl -O URL	Save with remote filename
curl -u user:pass URL	Basic authentication
curl -H "Header: Value" URL	Add header
curl -v URL	Verbose output
curl -L URL	Follow redirects
curl -k URL	Skip SSL verification

Common Examples

# POST JSON data
curl -X POST -H "Content-Type: application/json" \
  -d '{"key":"value"}' URL

# Upload file
curl -F "file=@localfile.txt" URL

# Download with resume
curl -C - -O URL

# Use proxy
curl -x http://proxy:port URL

# Follow redirects
curl -L -O http://example.com/file

# Check HTTP status code
curl -o /dev/null -s -w "%{http_code}" URL

Wget

COMMAND	DESCRIPTION
wget URL	Download file
wget -c URL	Continue interrupted download
wget -O filename URL	Save to specific filename
wget -r URL	Recursive download
wget -b URL	Background download
wget -c -r URL	Recursive with resume

Netcat

COMMAND	DESCRIPTION
nc -l 8080	Listen on port 8080
nc -l -p 8080	Listen on port 8080
nc -zv host 80	Check if port is open
nc -zv host 1-100	Scan ports 1-100
nc host port	Connect to host:port
`echo "message"	nc host port`
nc -l -p 8080 < file	Send file

Netstat

COMMAND	DESCRIPTION
netstat -tuln	List listening TCP/UDP ports
netstat -tulpn	List listening ports with process
netstat -an	List all connections
netstat -r	Show routing table
netstat -i	Show network interfaces

ss (Socket Statistics)

COMMAND	DESCRIPTION
ss -tuln	List listening TCP/UDP ports
ss -tulpn	List listening with process
ss -s	Show statistics
ss -4	IPv4 sockets
ss -6	IPv6 sockets

ip

COMMAND	DESCRIPTION
ip addr	Show IP addresses
ip link	Show network interfaces
ip route	Show routing table
ip link set dev eth0 up	Bring interface up
ip link set dev eth0 down	Bring interface down
ip addr add 192.168.1.2/24 dev eth0	Add IP address
ip addr del 192.168.1.2/24 dev eth0	Remove IP address
ip route add default via 192.168.1.1	Add default route

Tcpdump

COMMAND	DESCRIPTION
tcpdump -i eth0	Capture on interface
tcpdump -i eth0 -n	No DNS resolution
tcpdump -i eth0 port 80	Capture HTTP traffic
tcpdump -i eth0 host 192.168.1.1	Capture from specific host
tcpdump -i eth0 -w capture.pcap	Write to file
tcpdump -r capture.pcap	Read from file
tcpdump -i eth0 -v	Verbose output
tcpdump -i eth0 -c 100	Capture 100 packets

Filters

# Capture HTTP
tcpdump -i eth0 port 80

# Capture HTTPS
tcpdump -i eth0 port 443

# Capture from IP
tcpdump -i eth0 src 192.168.1.1

# Capture to IP
tcpdump -i eth0 dst 192.168.1.2

# Capture TCP
tcpdump -i eth0 tcp

# Capture UDP
tcpdump -i eth0 udp

# Capture ICMP
tcpdump -i eth0 icmp

# Capture with host and port
tcpdump -i eth0 host 192.168.1.1 and port 80

# Capture with OR
tcpdump -i eth0 "port 80 or port 443"

# Capture with NOT
tcpdump -i eth0 not port 22

Wireshark

Useful Display Filters

# HTTP
http

# HTTPS
tls

# TCP
tcp

# UDP
udp

# Filter by IP
ip.addr == 192.168.1.1

# Filter by port
tcp.port == 80

# Filter by host and port
ip.addr == 192.168.1.1 and tcp.port == 80

# Filter by protocol
tcp or udp

# Filter by network
ip.src == 192.168.1.0/24

Nmap

COMMAND	DESCRIPTION
nmap host	Scan host
nmap -p 80,443 host	Scan specific ports
nmap -p 1-1000 host	Scan port range
nmap -A host	Aggressive scan
nmap -sV host	Service version detection
nmap -O host	OS detection
nmap -T4 host	Faster scan
nmap -sS host	SYN scan (default)
nmap -sU host	UDP scan

Examples

# Quick scan (common ports)
nmap -F host

# Comprehensive scan
nmap -A -T4 host

# Scan network
nmap 192.168.1.0/24

# Scan with specific ports
nmap -p 22,80,443,3306 host

# Scan multiple hosts
nmap host1 host2 host3

Telnet

COMMAND	DESCRIPTION
telnet host port	Connect to port
telnet host 25	Connect to SMTP
telnet host 80	Connect to HTTP

SSH

COMMAND	DESCRIPTION
ssh user@host	Connect to host
ssh -p port user@host	Connect on specific port
ssh -i key user@host	Use specific key
ssh -L 8080:localhost:80 user@host	Local port forwarding
ssh -R 8080:localhost:80 user@host	Remote port forwarding
ssh-keygen -t ed25519	Generate SSH key
ssh-copy-id user@host	Copy key to host

ARP

COMMAND	DESCRIPTION
arp -a	Show ARP table
arp -n	Show without DNS resolution
arp -d host	Delete ARP entry
arp -s host MAC	Add ARP entry

Route

COMMAND	DESCRIPTION
route -n	Show routing table
route add default gw 192.168.1.1	Add default route
route del default	Delete default route
route add -host 192.168.1.2 gw 192.168.1.1	Add host route

Useful Commands

Check if port is open

nc -zv host port

Find process using port

lsof -i :port

Get public IP

curl ifconfig.me
curl ipinfo.io/ip

Check internet connectivity

ping -c 4 8.8.8.8

Check DNS resolution

nslookup host
dig +short host

Speed test

curl -o /dev/null http://speedtest.tele2.net/100mb.img

Download and test speed

curl -o /dev/null -w "Speed: %{speed_download} bytes/sec" URL

Best Practices

• Use curl for HTTP operations
• Use dig for detailed DNS queries
• Use nc for port checking
• Use tcpdump for packet capture
• Use nmap for port scanning
• Use ssh-keygen for SSH keys
• Use ip instead of ifconfig (modern)
• Use ss instead of netstat (modern)
• Use tcpdump for troubleshooting
• Monitor network traffic
• Use proper firewalls

TIP

Use mtr (My Traceroute) for real-time network monitoring: mtr host.