Win10 Host network access blocked by CentOS guest

[DMArmoza]

I'm desperate for advise. This is the second time I've somehow messed up a local account on a Windows Host when using VirtualBox to support a Linux Guest OS. Somehow the VirtualBox upgrade process or my Windows system AntiVirus (McAfee) upgrade is messing up a viable local account on my Windows Host OS.

The first time this happened, I had a Windows 7 Host and a RHEL6 Guest. My Host was able to use the normal network adaptor to see the Internet from my local account, let's call it johndoe. The Guest OS could see the Internet through a normal NAT setting in VirtualBox network settings. I performed an upgrade of VB and something about the upgrade disabled the johndoe account on the Host from connecting to the Internet. The Host saw that the network was live, but troubleshooting seemed to indicate that the VBox adaptor was blocking it. The Admin account under Windows 7 was still able to see the internet. The Guest OS was able to see the Internet, but because I need the Host to use VPN I couldn't leave the johndoe account like that. I dug around looking for solutions or reasons for my dilemma. I tried uninstalling and reinstalling VBox, but I eventually had to create a new local account johndoe2 under Windows so I could access the Internet unimpeded (and move all my files and settings too).

Now I have a Windows 10 Host with a CentOS 7 Guest. They were both working fine, but I ran into the cut-and-paste bug that I read seemed to be part of v6.1.4. The recommendation was to downgrade (to v6.1.2). I made sure not to have my VPN connected. I backed-up my vdi files, and then uninstalled v6.1.4. The recipe I read (for performing a VBox down-grade), said I should clean up VBox "trash" in Program Files, which I did, so I would get a fresh install of v6.1.2. I then disconnected my machine from the Internet, uninstalled my McAfee A/V, installed v6.1.2, rebooted, and then re-installed the A/V, rebooted, and re-connected to the Internet. I logged into johndoe2, and found I couldn't access the Internet from the Host anymore. The Host was seeing the Internet, but I was getting the same kind of VBox network adaptor warning from the trouble-shooter (on Windows) that seemed to indicate that it was hijacking my johndoe2 account's access like the previous time.

Does anyone have any ideas what could be causing this problem? I really don't want to move all my stuff to another local account to avoid this problem.

[scottgus1]

This situation is very unusual. Lots of users up/downgrade Virtualbox without having network issues or killed accounts. (or at least if they are they don't tell us about it ).

One diagnosing issue to consider is that switching accounts fixes the network glitch. If you went to your new account and started Virtualbox, register a guest, and try the guest, I'd wager that you have both host, VPN, and guest internet running fine. If you try this and it works, it would indicate that the underlying structure of Virtualbox and your network system are working fine, and there is a per-account setting or error in another program that is knocking out your host internet on the dead accounts.

Two things I see that might interfere are McAffee and the VPN. I had McAffee for a while, and it does dig deeply (oppressively in my opinion) into the functioning of the computer. VPNs also rule the network with an iron fist and have been known to interfere with Virtualbox. That the forum hasn't blown up with posts of Virtualbox destroying user accounts indicates that there's a world-wide Illuminati conspiracy to hide these issues from the forum , or it's a very rare problem and it's probably some other software on your PC that's causing it. I lean a little toward the second thought.

A troubleshooting test: Remove Virtualbox, Mcaffee and the VPN, Then reboot. Windows 10 comes with a good antivirus built-in (again, in my opinion, fwiw) so you should be safe with with active network and internet during this test. Test that you have good internet. Then install Virtualbox and run a guest, testing internet in the guest. Then add the VPN. Test internet host & guest again. At this point you should have a safe PC, using Windows built-in AV. Now add McAffee if you want to.

As for a preventative step, you might guess I'd say go McAffee-less. But you might also try uninstalling McAffee before uninstalling Virtualbox for a version change. Additionally, don't upgrade Virtualbox until you need to. "If it ain't broke..." etc. Finally, take reliable full and differential/incremental disk images, so if an account dies again, you can just restore rather than have to make a new account.

[mpack]

IME, this kind of problem is usually a result of the user messing with the network config in some dumb way, for example assigning the host MAC address to the VM, or similarly assigning host name or a static IP address matching that of the host or some other device on the local network. All routing services on the host get thoroughly confused by the duplication of supposedly unique identifiers.

[DMArmoza]

mpack, you might have had this experience in the past, but it seems unfair and vaguely insulting to conflate my problem as one by a user "messing with the network config in some dumb way". I am only using default network settings, and normal applications with default installations. I had my VM set up with NAT and that was it. I use my employer's purchased VPN client (Cisco AnyConnect) to communicate with a private work network, and use relatively benign local Windows account protections (via McAfee & Windows 10) in which I have successfully run VirtualBox for several years. Granted something in my local account is confused, and that was the purpose for my post. To solicit questions/advice as to what I could look at on my system, so as to discover the underlying cause.

I would gladly appreciate it if you have any helpful recommendations to solve this problem.

[DMArmoza]

scottgus1, thanks for your detailed response. I appreciate that my situation is very unusual, since I normally don't have to post to ask for help Just to be clear, I didn't want to try the down-grade of VB in the first place, but I really wanted cut-and-paste to work. According to what I found on the Internet, it seemed to be a problem with v6.1.4 and not v6.1.2, so that was why I ended up mucking with a working configuration.

I did switch accounts (per my johndoe and johndoe2 comments in my OP) and I did observe normal behavior which gave me some small level of comfort. Re-creating an account is much easier than rebuilding an OS, at least from my perspective, even though I would prefer to avoid both. I suspect it is something with McAfee too, but I do need to have an A/V solution that is approved by my employer so ditching it is not really OK. I

I'll try your trouble-shooting test out, and see if that gives me any help or better indications of what is going wrong.

[mpack]

@DMArmoza: there's no need for you to quote previous posts verbatim, they are right there above yours when we want to read them.