I opened a similar post weeks ago but it was not clearly put. Then it was moved to another board. Now I'm re-opening a post here, with more "proof" and hopefully better description.
Hardware/software: Laptop-1 (Ubuntu 14.04 with multiple windows guest VMs including XP, Win7 and Win10), Laptop-2 (Native Win10)
Network (all through WIFI): wired network through ISP-1, wired network through ISP-2, Android hotspot through ISP-3, Android hotspot through ISP-4, Android hotspot through ISP-5
System setting: Everything is by default
Problem:
1. In Win10, in the system tray, the network icon is with a yellow triangle and an exclamation mark. The system setting shows "no internet connection". However, most applications do not have problem with internet, except very few ones. i.e. actually the internet connection is there, but not fully recognized. I can open webpages in browsers, check emails, listen to music... except for some cases like Microsoft user account validation.
2. This only happens on Laptop-1, Win10 guest under Ubuntu with ISP-1, ISP-3, or ISP-4.
3. No problem with Laptop-2, as it's native Win10. So I guess it's not the problem of Win10.
4. No problem with Laptop-1 if connected with ISP-2 or ISP-5.
5. No problem with Ubuntu host system with any other application or any ISP. So I guess it's not the problem of Ubuntu.
6. No problem with Win7/XP guest system, or more precisely, no equivalent cases under Win7/XP.
7. After the guest Win10 is started with ISP-2 or ISP-5, i.e. with good internet connection, as long as the guest Win10 is not shut down, I can switch the host internet connection to any other ISP without causing any problem in the guest Win10. i.e. after I started Win10 guest with good internet connection and keeps Win10 running, this problem will disappear. I can even hibernate/suspend the HOST Ubuntu system without dealing with the running Win10 VM, and then resume without any problem. But if the Win10 VM is shut down, restarted, broken, or even powered off with saved machine state, the problem with be back after restart, if ISP-2 or ISP-5 is not connected.
What I've already tried: (none is working)
1. Disable IPV-6
2. Specify a DNS server
3. Change the default speed (or something like that)