Linux Ethernet Bridging - Jan 2009 - [Bridge] Network with some switches without STP/RSTP support

I have a network with three RSTP enabled swithes connected to form a
triangle (a ring with three nodes).
Let us say the switches are A, B , C
B and C are not connected with simple ethernet cable but they are
connected through an additional
small switch that doesn't support STP/RSTP. This simple switch has 3 ports,
one is connected to B,
another to C and the third port to a PC.

Does the RSTP will manage to resolve the loop (open the ring)? Will I manage
to reach anyway the PC?

Thank you in advance,
Antonio.
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On Fri, Jan 09, 2009 at 11:01:19PM +0100, Antonio Di Bacco
wrote:
> Does the RSTP will manage to resolve the loop (open the ring)? Will I
manage
> to reach anyway the PC?
Probably yes, but the answer could be no.  All the non-STP switches I've
ever seen do forward BPDUs.

Strictly speaking, 802.1D bridges should never forward frames addressed
to the reserved bridge management MAC addresses.  This would lead both
B & C to believe they were connected to an edge port, which will never
block.


-- 
Ross Vandegrift
ross at kallisti.us

"If the fight gets hot, the songs get hotter.  If the going gets tough,
the songs get tougher."
	--Woody Guthrie

"Antonio Di Bacco" <a.dibacco at gmail.com> writes:
> Does the RSTP will manage to resolve the loop (open the ring)? Will I
> manage to reach anyway the PC?
If you have connections A <=> B, B <=> C, C <=> A then
you'll have to
be very careful with your configuration if you want to ensure that the
link B <=> C isn't picked as the one to block. I would strongly
recommend that you don't make a topology that only works if certain
links are never blocked.

The best way to have that level of control is to disable spanning tree
and do the blocking/unblocking manually.


/Benny