== 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 ''(this is valid for releases prior VirtualBox 4.0)''.[[BR]]

'''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.