anthony morris
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Network Troubleshooting

ping

  • Packet Internet Groper
  • Used to verify that TCP/IP is:
    • Installed
    • Bound to NIC
    • Configured correctly
    • Communicating with the network
  • Sends out a signal called an echo request to another device
    • Other device responds with an echo reply
  • ICMP
    • Internet Control Message Protocol
    • Protocol used by echo request/reply
    • Carries error messages and info about the network
  • For IPv6
    • ping6 on Linux
    • ping -6 on Windows

ipconfig (Windows)

  • Shows current TCP/IP addressing and domain name info
  • ipconfig /all shows complete summary

ifconfig (Linux)

  • Utility to view/manage TCP/IP settings

nslookup

  • Name space lookup
  • Allows you to query DNS database from any computer on a network
    • Used to find host name of a device by specifying its IP address (or vice versa)
    • Useful for verifying a host is configured correctly
    • Useful for troubleshooting DNS resolution problems
  • Reverse DNS lookup
    • Find host name of device whose IP address you know

dig (Linux)

  • Domain Information Groper
  • Provides more detailed information than nslookup
  • Uses more reliable sources of info to output its results

netstat

  • Displays TCP/IP stats and details about TCP/IP components/connections on a host
  • Information that can be obtained:
    • Port on which TCP/IP service is running
    • Which network connections are currently established for client
    • How many messages have been handled by a network interface since activated
    • How many data errors have occurred on a particular network interface

tracert (Windows)

  • Uses ICMP echo requests to trace path from one networked node to another
  • Identifying all intermediate hops between nodes
  • Employs trail/error approach to discover nodes at each hop from source --> destination

traceroute (Linux, Unix)

  • Uses UDP messages to a random port on destination node (same concept as tracert)
  • Employs trail/error approach to discover nodes at each hop from source --> destination

Computer Science Networking