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cal
Asked: 2021-03-27 05:31:24 +0800 CST

why is ubuntu assigning ip 127.0.0.1

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I cannot figure out why ubuntu 18.04 is assigning a ip address of 127.0.0.1

I set my netplan

network:
    version: 2
    renderer: networkd
    ethernets:
        enp3s0:
            dhcp4: true

any tips welcome

netplan

1 Answers

  1. 127.0.0.1 is a loopback adress. Every machine has it (windows, linux, mac, android, litterly every device). It is called localhost and it is used quite often.

    Example 1 (let's assume server ip adress is 192.168.2.15):

    You have a web server on a computer running and you want to view the website it's hosting. From a different computer, you go to 192.168.2.15:80 in google and you'll see the webpage your server is hosting.

    Now you want to access the webpage from the server (aka access the webpage the server is hosting, from that server). Instead of typing the ip adress of the server (which will make the server connect to itself ofcourse), you can just type 127.0.0.1:80 and that will give you access. Because 127.0.0.1 (aka localhost) is... the server itself. You can also type localhost:80.

    Example 2:

    You have Prometheus (gathers info about your computer) and Grafana (makes nice graphs out of the info of Prometheus) installed. While setting up Grafana, you need to make a connection to Prometheus so that Grafana can use the info Prometheus is gathering to show it in a nice graph. When you have Prometheus and Grafana installed on the same computer, you can type localhost:9100/metrics in grafana to make a connection to Prometheus.

    Example 3:

    You have a Minecraft server running on a computer. Now you want to play on your new cool minecraft server ofcourse. If you want to play on the computer that the server is being run on, when adding a server, you can just type localhost and it will connect to the minecraft server running on itself.

    If you understand it correctly, you should be able to understand this:

    "ping localhost will always work."

    Just remember:

    localhost = 127.0.0.1 = itself

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