Multicast/mDNS/cast stops working after Wi-Fi reconnects
Date Added: 5/3/2022

Problem:
In the Google Chrome browser, the Cast feature sometimes does not show any cast targets while you're using Wi-Fi.

Each of these things will cause the problem:
* enable airplane mode, then disable it
* switch Wi-Fi networks (select a different SSID)
* lose Wi-Fi signal for any reason, and then regain it

Each of these things will work around the problem:
* reboot the laptop
* disable then re-enable the wireless NIC in Device Manager
* plug in with ethernet cable instead of using Wi-Fi

Technical Details:
My laptop's OS is Windows 10 Version 21H1, NIC is Intel Wireless-AC 8265, and NIC driver is the latest version which is v22.130.0 from 3/25/2022 and appears as v22.70.30.1 in Windows.  I did packet traces from the laptop and my router, and found that the laptop does send IPv4 and IPv6 mDNS (multicast) requests to 224.0.0.251, from port 5353 to port 5353.  The recipient receives the request and replies with the normal response (the response is supposed to tell the laptop the IP Address of the cast target).  But, the laptop does not seem to acknowledge that reply.  My guess is that Windows or the NIC driver forgets to listen on IP address 224.0.0.251 whenever it reconnects to Wi-Fi.  It seems like a very simple fix to make the NIC listen to multicast after a reconnect, but, Microsoft.

I tried changing ALL of my NIC's driver settings (in Device Manager) to each of their other options, and none of that had any improvement.

Cause:
Apparently, Microsoft has been aware of this Windows bug since at least 2020:

"The engineering team has investigated this multicast issue with Microsoft. Microsoft is aware there's an issue with the multicast address managed by the OS. The issue has been introduced together with Windows 10 (WDI arch for WiFi Drivers.) Any scenarios of WLAN reconnected (i.e. Airplane mode, roaming out and back into RF range, or disconnect and reconnect to the same SSID) and then the multicast packets might be affected by this issue.
Currently this issue is expected to be fixed for Windows 10 Version 21H1."

(Note: as of May 2022, on Windows 10 version 21H2, the problem remains)

References:
https://docs.microsoft.com/en-us/answers/questions/101168/mdns-not-sending-queries-to-the-network.html
https://superuser.com/questions/1548592/how-to-continually-run-mdns-on-windows-10

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