brctl setfd virbr0 0.1 by default?

[Don Dutile]

Warren Togami wrote:
> Daniel P. Berrange wrote:
>> On Mon, Jul 21, 2008 at 04:06:50PM -0400, Warren Togami wrote:
>>> https://bugzilla.redhat.com/show_bug.cgi?id=435757
>>> 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?
> 

Try reducing the delay to 0.  I believe this is the same/similar issue that
Herbert Xu is dealing with when xen guests are migrated, and the guest doesn't
see the network for some number of seconds.  
I'm trying to find the BZ & thread that had this info in it, but searching
through xen-maint bz's is not turning up what I'm looking for.
BZ 441716 proposes another solution for rhel5; not sure if fedora needs it as well.

- Don

> Warren Togami
> wtogami at redhat.com
>