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How To Debug Network, A Small Toobox

·166 words·1 min
tips&tricks
Author
Fungal
Borned to be fungus, forced to be mushroom. she/her
Table of Contents

With time and experience you learn how to debug things more efficiently, and make your own “toolbox”. Here’s a list of things I want to share when needed. I’ll try to keep it updated with my new findings.

Adapt commands to your needs, I’m writing from an average linux distro point of view.

Does The Internet Routing Work?
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These are the shortest IP I could ever find.

ping 1.1
ping 2600::

Does DNS Work?
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Works with IPv6 and legacy IP.

dig c.im

Is The Port Open?
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Knocks a port (TCP) and timeouts if it takes longer than 5 seconds.

nc -vzw5 <target> <port>

Various Tools
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  • wireshark, awesome protocol and frame analyser
  • tcpdump, great to see what’s happening on the wire. You can save capture as pcap and read using Wireshark
  • mtr, ping and traceroute merged in a single tool

Notes
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  • it’s not because a ping works that TCP is not filtered by the firewall; ping is ICMP which is not TCP