On 04/10/2011 06:32 PM, Serge Hallyn wrote: Yes, it's already been addressed, The following commit was included in 0.9.0: commit 5754dbd56d4738112a86776c09e810e32f7c3224 Author: Laine Stump <laine(a)laine.org&gt; Date: Wed Feb 9 03:28:12 2011 -0500 Give each virtual network bridge its own fixed MAC address This fixes https://bugzilla.redhat.com/show_bug.cgi?id=609463 The problem was that, since a bridge always acquires the MAC address of the connected interface with the numerically lowest MAC, as guests are started and stopped, it was possible for the MAC address to change over time, and this change in the network was being detected by Windows 7 (it sees the MAC of the default route change), so on each reboot it would bring up a dialog box asking about this "new network". The solution is to create a dummy tap interface with a MAC guaranteed to be lower than any guest interface's MAC, and attach that tap to the bridge as soon as it's created. Since all guest MAC addresses start with 0xFE, we can just generate a MAC with the standard "0x52, 0x54, 0" prefix, and it's guaranteed to always win (physical interfaces are never connected to these bridges, so we don't need to worry about competing numerically with them).