When troubleshooting a network, there are several command-line tools available for diagnosing and resolving issues. Here’s a comprehensive list of network troubleshooting commands commonly used in both Windows and Linux/Unix environments. These commands help you identify problems with connectivity, latency, DNS, routing, and more.

1. Basic Connectivity and Latency Tests

Ping

• Windows/Linux/Unix: ping [destination IP or domain]
  • Tests the reachability of a host and measures round-trip time.
  • Example:
    ping google.com

    ping 192.168.1.1

Traceroute / Tracert

• Windows: tracert [destination IP or domain]
• Linux/Unix: traceroute [destination IP or domain]
  • Traces the path packets take to reach the destination and identifies where delays or failures occur.
  • Example:
    tracert google.com
traceroute google.com


MTR (My Traceroute)

• Linux/Unix: mtr [destination IP or domain]
  • Combines the functionality of ping and traceroute to provide a real-time report of network latency and packet loss across multiple hops.
  • Example:
    mtr google.com


2. DNS Troubleshooting

Nslookup

• Windows/Linux/Unix: nslookup [domain name]
  • Queries DNS servers to resolve domain names into IP addresses and troubleshoot DNS issues.
  • Example:
    nslookup google.com
nslookup 8.8.8.8


Dig (Domain Information Groper)

• Linux/Unix: dig [domain name]
  • A more powerful DNS lookup tool with extended capabilities compared to nslookup.
  • Example:
    dig google.com
dig @8.8.8.8 google.com


Host

• Linux/Unix: host [domain name]
  • Performs DNS lookups and provides a straightforward way to query DNS records.
  • Example:
    host google.com
host 8.8.8.8


3. Routing and IP Configuration

IPConfig (Windows)

• Windows: ipconfig [options]
  • Displays network adapter configurations, including IP addresses, subnet mask, and gateway.
  • Example:
    ipconfig
ipconfig /all
ipconfig /release
ipconfig /renew


Ifconfig (Linux/Unix)

• Linux/Unix: ifconfig
  • Displays or configures network interfaces and their IP addresses.
  • Example:
    ifconfig
ifconfig eth0


IP (Linux/Unix)

• Linux/Unix: ip [options]
  • Replaces ifconfig in many modern Linux distributions. It can be used to configure network interfaces, routing, and IP addresses.
  • Example:
    ip a
ip link show
ip route show


Route (Windows/Linux/Unix)

• Windows: route print
• Linux/Unix: route -n
  • Displays the routing table, which shows how traffic is routed to different networks.
  • Example:
    route print
route -n


4. Network Interface and Packet Capture

Netstat

• Windows/Linux/Unix: netstat [options]
  • Displays active network connections, routing tables, interface statistics, and more.
  • Example:
    netstat -a
netstat -tuln
netstat -r


Tcpdump

• Linux/Unix: tcpdump [options]
  • Captures packets on a network interface and allows analysis of traffic.
  • Example:
    tcpdump -i eth0
tcpdump -i eth0 port 80
tcpdump -i eth0 -w capture.pcap


Wireshark (GUI tool)

• Linux/Unix/Windows: Wireshark is the GUI version of tcpdump, but you can run it from the command line with tshark.
  • Example:
    tshark -i eth0
tshark -r capture.pcap


5. Testing Network Performance

Iperf

• Windows/Linux/Unix: iperf3
  • Measures the bandwidth between two hosts. You need to run the iperf server on one host and the client on the other.
  • Example:
    iperf3 -s # On server
iperf3 -c [server IP] # On client


Speedtest-cli

• Linux/Unix: speedtest-cli
  • A command-line tool for testing internet speed using Speedtest.net servers.
  • Example:
    speedtest-cli


6. TCP/IP Stack and Firewall Troubleshooting

Telnet

• Windows/Linux/Unix: telnet [hostname or IP] [port]
  • Tests if a specific port on a host is open and accessible.
  • Example:
    telnet google.com 80
telnet 192.168.1.1 22


SSH

• Linux/Unix/Windows: ssh [user]@[hostname or IP]
  • Securely connects to a remote system for troubleshooting and administration.
  • Example:
    ssh user@192.168.1.1


Curl

• Linux/Unix/Windows: curl [options] [URL]
  • Makes HTTP requests and can be used to check web server status or retrieve data from URLs.
  • Example:
    curl google.com
curl -I google.com


Firewall (Windows/Linux/Unix)

• Windows: netsh advfirewall firewall show rule name=all
• Linux/Unix: iptables -L
  • Checks firewall rules that could block network traffic.
  • Example:
    iptables -L


7. Checking for Packet Loss or Errors

Ping with Packet Size

• Windows/Linux/Unix: ping -l [size] [destination] (Windows) or ping -s [size] [destination] (Linux)
  • Helps check if the network is dropping packets or having issues with larger payloads.
  • Example:
    ping -l 1500 google.com # Windows
ping -s 1500 google.com # Linux


Pathping (Windows)

• Windows: pathping [destination IP or domain]
  • Combines ping and traceroute, providing both route and packet loss information.
  • Example:
    bash

    pathping google.com


Netcat (nc)

• Linux/Unix/Windows: nc [options]
  • A versatile network utility for debugging and investigating the network, including port scanning and banner grabbing.
  • Example:
    bash

    nc -zv google.com 80
nc -l 12345


8. Checking ARP Table

ARP (Address Resolution Protocol)

• Windows: arp -a
• Linux/Unix: arp -n
  • Displays or modifies the ARP (Address Resolution Protocol) table, showing IP-to-MAC address mappings.
  • Example:
    arp -a
arp -n


Summary of Common Network Troubleshooting Commands: