Network tracing

Network problems could be detected by enabling packet logging at the guest side or at the host side, but using the built-in capability of VirtualBox to create pcap files might provide even more useful information because it contains a log of really all packets received and sent by guest.

To enable network tracing do the following:

# VBoxManage modifyvm [your-vm] -nictrace[adapter-number] on -nictracefile[adapter-number] file.pcap
# VirtualBox -startvm [your-vm]

For example

# VBoxManage modifyvm "ubuntu" -nictrace1 on -nictracefile1 file.pcap
# VirtualBox -startvm "ubuntu"

Note: Don't forget to disable tracing after you finished the investigation because your hard disk will quickly be filled by pcap files in case of intensive network usage. The port-forwarding configuration might be affected by this setting as well.

Note: If the situation is 100% reproducible and it takes some time to reproduce, the following steps are recommended to create the pcap file:

1. Prepare the environment to test, "lead" your application very close to the state when the problem appears.
2. Press host-S (take a snapshot).
3. Press host-Q, select shutdown with discard to snapshot.
4. Run the VM again and finish the test.