Subject: [rbridge] Rbridge setting of BPDU Topology Change Flag

From: "Eastlake III Donald-LDE008" <[email-masked]>
Date: Tue, 27 May 2008 14:54:35 -0400

Assume a bridged LAN with one or more bridges in connected to an Rbridge
port. The bridges in that bridged LAN will, in general, learn MAC
addresses based on native frames sent out that port by the Rbridge. When
the appointed forwarder status of that Rbridge port changes, it seems to
me it would be polite for the Rbridge to send a BPDU with the topology
change flag set so as to clear MAC address cache entries in the
bridge(s) that may no longer valid.

Donald
====================================================
 Donald E. Eastlake 3rd      +1-508-786-7554 (work)
 Motorola Laboratories
 111 Locke Drive
 Marlborough, MA 01752 USA
 [email-masked]

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From: Radia Perlman <[email-masked]>
Date: Wed, 28 May 2008 16:34:46 -0700

This seems harmless and, as you said, polite. I think it should be a 
SHOULD. For a bit more explanation,
it's for bridges inside the link that have learned the direction of 
destinations off the link. A bridge was
thinking that D was in the direction of the previous VLAN forwarder, so 
if S (on the link) is
talking to D (off the link), a bridge might not forward it to the new 
VLAN forwarder, and D might
therefore not receive the traffic.

The topology change notification tells the bridges on the link to switch 
to a short cache timer, getting
rid of incorrect cache entries fairly quickly.

Radia