I'm using VirtualBox (the latest version) on a Windows 7 workstation. The VM is configured with 4GB of RAM and 2 cores, and VT-x is enabled. The network adapter is configured as a bridged adapter.
I first noticed the problem because I was using the ResourceSpace site and it suddenly timed out. After restarting, it worked for a while, then again suddenly stopped. I began troubleshooting and found that it was losing network connectivity after a few minutes.
It's not a DNS issue, the network is completely unusable after five minutes, can't ping the machine, can't ping other resources from within the machine.
ifconfig is not installed with this package, but ip addr returns the results shown below.
Immediately after boot, the machine has network access. Interface enp0s3 has an IPv4 addess, and I can access the machine over the network.
Exactly five minutes after booting up, the network stops responding, and running ip addr shows that there is no longer an IPv4 address for the interface.
If I look in /var/log/error I see the following messages...
dhclient Failed to get interface index: No such device.
systemd: Failed to start Raise network interfaces.
It seems like some things on the machine are trying to use eth0, but that interface doesn't exist. Not sure if that is related.