Shane Rainville
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How to Configure Debian 9 Network Settings

Debian 9 network settings

This tutorial will walk you through configuring your network setting for Debian 9 Stretch.  I will show you how to set static address and dynamic address for IPv4 and IPv6.

GNOME Desktop

The default desktop environment for Debian 9 Stretch is GNOME 3. We will focus on this environment,

IPv4 Static Address

IPv4 DHCP

IPv6 Static Address

IPv6 DHCP

Terminal

For more advanced users and those running a GUI-less server, the following instructions will aid you.

All configuration can be found under /etc/network. You may either define all of your interfaces in a single file or place them in individual files under /etc/network/interfaces.d.

Understanding Network Interface Names

Most recent distributions have switched over to predictable naming. Prior to this an interfaces name was derived from the order it was discovered; the first interface would be named eth0, the second eth1, and so on. The problem with this approach is eth0 wasn’t always the same slot, making troubleshooting difficult.

I cover this topic in much more detail in Understanding Predictive Interface Naming in Linux. For most, the naming convention would be the following:

<interface type><bus number><slot number>

For example, an Ethernet interface – the most common – found on bus 0 and slot 3 of your motherboard would be named:

enp0s3

IPv4 Static Address

  1. Open the network interface configuration file into a text editor, such as VI.
  2. Add the following lines. 
    auto enp0s3
iface enp0s3 inet static
address 192.168.1.20
netmask 255.255.255.0
gateway 192.167.1.1
  3. Save your changes and exit the text editor.
  4. Bring the interface down. 
    ifdown enp0s3
  5. Bring the interface back up. 
    ifup enp0s3
  6. Verify your network settings have been applied. 
    ip a

IPv4 DHCP

  1. Open the network interface configuration file into a text editor, such as VI.
  2. Add the following lines. 
    auto enp0s3
iface enp0s3 inet dhcp
  3. Save your changes and exit the text editor.
  4. Bring the interface down. 
    ifdown enp0s3
  5. Bring the interface back up. 
    ifup enp0s3
  6. Verify your network settings have been applied. 
    ip a

IPv6 Static Address

  1. Open the network interface configuration file into a text editor, such as VI.
  2. Add the following lines. 
    auto enp0s3
iface enp0s3 inet6 static
address fd9f:2685:51fa:2e4e:xxxx:xxxx:xxxx:xxxx
netmask 64
gateway fd9f:2685:51fa:2e4e:xxxx:xxxx:xxxx:xxxx
  3. Save your changes and exit the text editor.
  4. Bring the interface down. 
    ifdown enp0s3
  5. Bring the interface back up. 
    ifup enp0s3
  6. Verify your network settings have been applied. 
    ip a

IPv6 DHCP

  1. Open the network interface configuration file into a text editor, such as VI.
  2. Add the following lines. 
    auto enp0s3
iface enp0s3 inet6 auto
  3. Save your changes and exit the text editor.
  4. Bring the interface down. 
    ifdown enp0s3
  5. Bring the interface back up. 
    ifup enp0s3
  6. Verify your network settings have been applied. 
    ip a

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