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NetworkManager

lastmod 2026-03-22created 2015-07-0615 edits

NetworkManager is a daemon that runs on top of libudev and other Linux kernel interfaces, and provides a high-level interface for configuring network interfaces.

NetworkManager is a software utility that aims to simplify the use of computer networks. NetworkManager is available on Linux kernel-based and other Unix-like operating systems.

Categories

route

Linux Routing Table 

route -n

Meaning of each field:

  • Destination - destination network
  • Gateway - gateway address for reaching the destination
  • Genmask - netmask address of the destination network (the result of ANDing the destination IP with the Genmask is the destination network) - if this is the same, they conflict!!!
  • Flags - symbols giving information about the route
    • U - up
    • H - destination is a Host
    • G - uses a gateway
  • Metric - distance to the destination network
  • Ref - number of times the route was referenced
  • Use - number of times the route was looked up
  • IFace - network interface

NetworkManager.conf

How to configure IPs in different ranges to communicate with each other

See Internet Protocol#How to configure IPs in different ranges to communicate with each other.

Hotspot Login: http://nmcheck.gnome.org/

When Wi-Fi connects, http://nmcheck.gnome.org/ shows up along with the text "Hotspot Login". What is this?

nmcheck.gnome.org is the Captive Portal detection URL that NetworkManager connects to automatically to check the internet connection status.

How it works

When connecting to WiFi, NetworkManager sends an HTTP request to the URL below in the background.

http://nmcheck.gnome.org/check_network_status.txt

It determines the connection status based on the response.

Response

Verdict

Normal response (200 OK)

Connected to the internet

Redirect occurs (302, etc.)

Captive Portal detected (public WiFi requiring login)

No response / timeout

Internet blocked

Hotspot Login popup

When NetworkManager detects a Captive Portal, a feature that automatically opens the login page kicks in.

  • Used on networks that require login, such as café, hotel, and airport WiFi
  • Pops up automatically without the user having to open a browser manually

Disabling

Add the following to /etc/NetworkManager/NetworkManager.conf. 

[connectivity]
enabled=false

After configuring, restart NetworkManager. 

sudo systemctl restart NetworkManager

Changing the detection URI

If you are concerned about privacy, you can replace it with your own server's URL. 

[connectivity]
uri=http://your-own-server.example.com/check
response=NetworkManager is online

Disabling GNOME notifications 

gsettings set org.gnome.nm-applet disable-connected-notifications true

Privacy

  • Each time WiFi connects, a record of the connection attempt may be left on the gnome.org server
  • If it bothers you, replacing it with your own server or another URL using the URI change method above is recommended
  • It is not a security threat; it is simply a request to check the internet connection

See also

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