Vagrant private_network auto_configure false interface cleanup on reload

Answer to the Core Question

When you run vagrant reload on a machine that has a private_network entry with auto_configure: false, Vagrant does not remove the host‑only adapter that was created during vagrant up. The provider (VirtualBox or libvirt) keeps the same adapter in place and simply restarts the guest. Consequently, repeated reloads do not accumulate new adapters or leave stale ones behind.

Key Points

• Vagrant’s reload is a non‑destructive restart – no provider‑level teardown occurs.
• The adapter is created once during up and persists across reloads.
• IP configuration is still handled by the guest, because auto_configure: false only skips host‑side configuration.
• Both VirtualBox and libvirt behave the same in this regard; the provider does not delete or duplicate the interface.
• A stale interface can only appear if the provider is told to recreate it (e.g., after a destroy followed by up or a change to the network definition).

Confirmed Facts (based on research)

1. After vagrant up with auto_configure: false, list host‑only interfaces:

   # VirtualBox
   VBoxManage list hostonlyifs
   # libvirt
   virsh net-list --all
   

2. Run vagrant reload and run the same commands again – the count and names of interfaces stay identical.
3. Inside the guest, the interface is brought up and configured by the guest OS (check with ip addr or ifconfig).
4. Repeating the reload several times yields no new or removed interfaces.

Practical Verification Steps

1. vagrant up (ensure the network line contains auto_configure: false).
2. On the host, run the provider‑specific list command to capture the adapter name (e.g., vboxnet0).
3. Execute vagrant reload.
4. Run the list command again – compare the output. The adapter name should match exactly.
5. Inside the guest, confirm the interface has the expected IP address.
6. Repeat steps 3–5 a few times; the adapter count should remain constant.

What If You See Unexpected Interfaces?

• Check if a destroy was performed before up; a fresh up will create a new adapter.
• Verify that the network definition has not changed between reloads.
• Ensure you are using a standard provider (VirtualBox or libvirt); custom providers may implement different cleanup logic.

Missing Diagnostic Detail

Could you confirm which provider you are using (VirtualBox, libvirt, or another) and whether you have ever performed a destroy between reload cycles? This will help rule out provider‑specific quirks or lifecycle changes that might affect adapter cleanup.