Windows NCSI

Network Connectivity Status Indicator (NCSI)

Before marking a network interface as available for applications, Windows tries to resolve hard-coded domain names, as well as retrieve the content of http://www.msftncsi.com/ncsi.txt.

If these names resolve or if the HTTP downloading succeeds, NCSI reports the network interface as "Internet access". Or, the network alert appears in the Task Bar saying "No connectivity" or "Limited Internet access" (depending on which requests failed). More details: NCSI active probes and the network status.

This can be fixed by uncommenting the following line from the [captive_portals] section of the main configuration file:

map_file = 'example-captive-portals.txt'

example-captive-portals.txt, which can of course be renamed, is a file that maps test domain names to IP addresses.

For Windows, here's an example of what such a file can contain, even though the provided example should already be fine:

www.msftncsi.com                2.16.106.89, 2.16.106.91, 23.0.175.137, 23.0.175.146
dns.msftncsi.com                131.107.255.255, fd3e:4f5a:5b81::1
www.msftconnecttest.com         13.107.4.52
ipv6.msftconnecttest.com        2a01:111:2003::52

Also, change the system setting for NCSI to use global DNS, rather than MS's proprietary.

Queries for these names will instantaneously get a response, even before the operating system marks the network interface as available.