If_bridge and MST

Andrew Thompson thompsa at FreeBSD.org
Mon Sep 3 14:00:07 PDT 2007

On Mon, Sep 03, 2007 at 10:21:20PM +0100, Tom Judge wrote:
> Andrew Thompson wrote:
> >On Mon, Sep 03, 2007 at 02:11:59PM +0100, Tom Judge wrote:
> >>Hi,
> >>
> >>I was wondering if if_bridge had been taught how to speak multiple 
> >>instance spanning tree?
> >
> >Not yet. I havnt started it yet and I do not know of anyone else working
> >on it.
> >
> While playing with if_bridge today and a pair of Dell PowerConnect 
> 5324's (with the recent upgrade to MSTP) I noticed that it did not seem 
> to be possible to enable STP on if_vlan bridge members.  This would seem 
> to be correct as transmitting STP frames tagged with VLAN_ID would seem 
> to break the spec and fall into the realm of cisco PVST.  However should 
> if_bridge be taught that the vlandev should be used for collection and 
> transmission spanning tree in this scenario or should if_vlan be taught 
> to copy untagged [R]STP frames onto the vlan interface?

Would this make it work the same as Cisco PVST? I havnt looked into how
PVST works but whatever the solution is it would need to interoperate
with other vendors. Obviously MST support is ideal. Most of the code is
already there in the form of RSTP, and MST tacks a bit more info on the
end. To be honest I have found 802.1Q-2003 a bit unclear in this area.


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