Network Tools in Linux

Motivation

We have learned the basics of how a network works. Now lets look at more tools that help you debug and troubleshoot network issues.

DNS Lookup

When you go to a website you do not need to remember the IP address. You use a name for that. e.g. you go to www.google.com. In order to find the associated IP address you need to lookup that name. The tools for that are: host nslookup or dig. For simple lookups I prefer host, while the other tools will give you more detailed information of how the lookup worked.

 host www.google.com
www.google.com has address 172.217.16.196
www.google.com has IPv6 address 2a00:1450:4001:817::2004

Sometimes you want to define aliases for certain hosts. Especially in your private network at home you will not want to run your own DNS system. A simple file that relates IP addresses to names will be sufficient to make your life easiser. This is the /etc/hosts file where you can add names to your IP addresses. E.g. your hosts file could look like this:

$ cat /etc/hosts
127.0.0.1	localhost
::1     localhost ip6-localhost ip6-loopback

192.168.19.27 laptop1 acer
192.168.19.101 handy lg200
192.168.19.1 netgear