[libvirt-users] STP default behavior for bridged (off) and NAT (on) networking in libvirt

[Daniel P. Berrange]

On Thu, Apr 15, 2010 at 09:23:46PM +0200, Francesco Pretto wrote:
> 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

I don't believe we're recommending STP=off for bridging. Our recommended
config is

# cat > ifcfg-br0 <<EOF
DEVICE=br0
TYPE=Bridge
BOOTPROTO=dhcp
ONBOOT=yes
DELAY=0
NM_CONTROLLED=no
EOF

And IIUC, STP defaults to on if not specified.

I agree STP should always be on for bridging to avoid netloops. The main
important param DELAY=0 is there to ensure that you get instant network
connectivity when doing live migration - without it you'll get a 30 second
network blackout

Daniel
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