NAT nw issue for 1 linux VM on 6.1.32 (running on Win10 host)

Discussions about using Linux guests in VirtualBox.
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falcon74
Posts: 32
Joined: 4. Jun 2018, 20:02

NAT nw issue for 1 linux VM on 6.1.32 (running on Win10 host)

Post by falcon74 »

Hi,

Have 3 nearly identical VMs running Alpine Linux guest OS, on Virtualbox 6.1.32 on Windows 10 Enterprise, on my PC. I connect to internet over WLAN.
There was an identical change that was done to all 3 VMs after which only one of the three VMs seems to have some issues using the NAT network to reach internet.

Originally, all 3 VMs had two network interfaces, i.e. the first interface being 'NAT' and second interface being 'Internal Network'. Over the 'Internal Network' interface the 3 VMs could reach each other i.e. ping, traceroute, ssh etc. were working fine. Also, I could reach internet from each of the 3 VMs (over the 'NAT' interface). In the Alpine Linux guest OS's network configuration, the first interface i.e. eth0 was set to get IP/config over DHCP, but second interface i.e. eth1 was configured with static IP, subnet, gateway configuration.

Then, I made the same change on all 3 VMs, i.e. I swapped the order of the interfaces, with the 'Internal Network' being first and 'NAT' one being second. Made corresponding changes in the Alpine Linux guest OS's network configuration to reflect this change, i.e. eth0 now had the static IP, subnet, gateway configuration (since it was 'Internal Network'), and eth1 i.e. 'NAT' interface (second interface) was configured thru DHCP. After this change, 2 out of the 3 VMs continue to work perfectly fine, i.e. can reach each other (ping, traceroute, ssh) and also access the internet (over NAT interface), but the third one doesn't. The third VM can reach other 2 VMs over 'Internal Network', but cannot reach internet over NAT interface.

I've ensured that all VM's guest OS's have unique hostname, IP-address (for the static IP one) and also ensured that each one uses different MAC address (through VM Networking properties). I've tried quite a bit to troubleshoot the issue with the 3rd VM, but wondering if anyone had any clue as to what more one might look for ? For instance, is there any way to see if the 'NAT interface' on the 3rd VM is really being written-to/read-from ?

thanks,
B
scottgus1
Site Moderator
Posts: 20965
Joined: 30. Dec 2009, 20:14
Primary OS: MS Windows 10
VBox Version: PUEL
Guest OSses: Windows, Linux

Re: NAT nw issue for 1 linux VM on 6.1.32 (running on Win10 host)

Post by scottgus1 »

I'm no Linux guru, but I recall hearing of a network card priority something-or-other which makes the OS look to a certain card for network first. That may be present, and it may require a tweak. I have no idea if it is your problem or what it's called, though.

Since this is likely a config issue inside the VM OS, I'll move this to Linux Guests. Also consider looking on forums and help channels for the OS.
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