Network

Basic command line tools

• Get the list of the interfaces

  nmcli dev status
  

  Output of the command :

  nmcli dev status
  DEVICE     TYPE      STATE         CONNECTION
  enp0s31f6  ethernet  connected     Wired connection 1
  enp3s0     ethernet  connected     TOF sensor 1
  wlp9s0     wifi      disconnected  --
  enp10s0    ethernet  unavailable   --
  enp4s0     ethernet  unavailable   --
  enp7s0     ethernet  unavailable   --
  enp8s0     ethernet  unavailable   --
  lo         loopback  unmanaged     --
  

• Get all the current interfaces configuration

  ifconfig
  

• View the network routes

  ip route # All routes
  ip route | grep default # Default gw
  

• Set up an interface

  nmtui # run the NMTUI (Network Manager Text User Interface) and follow the steps on the screen
  

  Warning

  Do NOT use ifconfig to set up an interface, it is deprecated and does not always work (typically on our Spectra 1-2 with Ubuntu 18.04 )

• Set up the default gateway

  # Using route command
  $ sudo route add default gw <gw_ip_address>
  
  # Using ip command
  $ sudo ip route add default via <gw_ip_address>
  

Limitation of the ephemeral ports range

An ephemeral port is a short-lived port used by a program to communicate via an internet protocol to another program. It is allocated automatically from a predefined range.

The configuration file is located in /proc/sys/net/ipv4/ip_local_port_range. It is not possible to modify it with a text editor.

• Modify the range of ephemeral ports

  sudo sysctl -w net.ipv4.ip_local_port_range="58000 60999"
  

Note

It seems like it will be reset to original values after a reboot.

Advanced network configuration file

Located in /etc/netplan/ is a YAML file (often called config.yaml) that describes the network settings. It can be modified.

• The standard version means that the GUI is responsible for the settings

  To visualize it, run :

  cat /etc/netplan/*.yaml
  

  The output should be :

  network:
     version: 2
     renderer: NetworkManager
  

• To ensure the PC will follow a specified network configuration, it is possible to define for each interface its configuration. The content of the config.yaml file could for example looks like the following configuration :

  network:
     version: 2
     renderer: networkd
  
     # Static IP address for all Ethernet interfaces, with 255.255.255.0 as mask
     ethernets:
        enp3s0:
           addresses:
              - 192.168.0.100/24
           dhcp4: false
        enp4s0:
           addresses:
              - 192.168.1.100/24
           dhcp4: false
        enp7s0:
           addresses:
              - 192.168.2.100/24
           dhcp4: false
        enp8s0:
           addresses:
              - 192.168.3.100/24
           dhcp4: false
  
     # Connection to a secured WPA Enterprise Wifi
     wifis:
        wlp9s0:
           access-points:
              workplace:
                 auth:
                    key-management: eap
                    method: peap
                    identity: "login"
                    password: "pw"
           dhcp4: true
  

More examples about netplan can be found on netplan.io/examples.

• After modifying the YAML file, the following command must be run :

  sudo netplan apply
  

Linux Network