Network troubleshooting

Here are some basic commands to trouble shoot networking issues:

ping

ping <hostname>
  • send ICMP ECHO_REQUEST to network hosts
  • ping uses ICMP protocol (ports are only for TCP/UDP)
  • Check to see if a host is reachable from our computer

nmap

nmap -PN <hostname> -p <port(s>

netstat

netstat [--tcp] -p -l <hostname> 
sudo netstat -tapen | grep ":8000 " # find the process using port 8000
  • Print network connections
  • Find which process is using a certain port number

telnet

telnet <hostname> <port>
  • user interface to the TELNET protocol
  • Great for checking if a port is accepting connections
  • Possible to check login and send email through an smtp server

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Posted in Linux, Networking

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