brctl setfd virbr0 0.1 by default?

Warren Togami wtogami at
Tue Jul 22 14:22:12 UTC 2008

Daniel P. Berrange wrote:
> On Mon, Jul 21, 2008 at 04:06:50PM -0400, Warren Togami wrote:
>> Sometime after F8, something changed where stuff attached to a bridge 
>> fails to connect until 15 seconds later.  A manual workaround of brctl 
>> setfd BRIDGENAME 0.1 makes stuff work immediately.
>> Are there any reasons why don't we do this by default for virbr0 in libvirt?
> Because no one has ever suggested it before...
> Arguably we should just turn off STP on the virbr0 device. Since it is
> not connected directly to the public LAN[1] there is no risk of network
> loops and thus spanning tree protocol is pointless for virbr0. I wonder
> if somewhere along the lines post F8 GA, STP accidentally got toggled 
> from offf by default to on by default on virbr0. Please file a BZ about
> this problem.
> Daniel
> [1] The only connectivity is outbound, masqueraded / NAT traffic.

Disabling STP on virbr0 alone is not enough.  I just tested it now.  STP 
enabled or disabled, the default forward delay of 15 seconds makes it 
fail for 15 seconds, long enough for most DHCP clients to give up.

Given this, what should we do?  Both disable STP and also reduce the delay?

Warren Togami
wtogami at

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