Hello, when talking about networking in hypervisors, it's easy to distinguish the two classic configurations, NAT and bridged, and the official libvirt wiki does exactly in this way here [1]. NAT networking is already configured by libvirt creating a bridge called libvirt0, while bridged networking have to be configured manually by the user. The libvirt0 bridge for NAT networking is default configured in this way: STP=on MAXWAIT=0 While suggested br0 bridge for bridged networking is configured in this way: STP=off MAXWAIT=5 Please, can you explain me why STP is on for NAT and should be off for bridged networking? It seems much easier to me to create loops when using bridged networking than NAT. Moreover, reading this old debian bug about complaints of MAXWAIT != 0 when STP off, I'm wondering if the suggested configurations aren't actually switched. Thanks, Francesco [1] http://wiki.libvirt.org/page/Networking [2] http://www.mail-archive.com/debian-bugs-dist@lists.debian.org/msg700924.html