Multisource Detection is a feature that prevents network disruption due to excessive topology changes caused by a full duplex port transmitting multiple BPDUs with different source MAC addresses, and hence different BPDU information. When a port is point-to-point, the received priority information comes from the most recently received BPDU. When a port is non-point-to-point, the received information reflects the best priority information out of all the received BPDUs.
Typical scenarios for multisource detection are when a switch is connected to a device which:
In these situations, the connected port is effectively acting as a shared media device. Shared media is detected using the duplex setting. Since the port is full duplex it treats the connection as point-to-point.
One way of preventing the disruption of this situation is to configure the receiving port‘s adminpoint value to false. This causes the operpoint value to always be false and to be treated as non-point-to-point. Multisource Detection, which is always enabled, recognizes the multiple source MAC addresses and automatically sets the operpoint value to false when the adminpoint value is auto. The port is constantly monitored. If the situation is resolved, as determined by receiving a unique address for a sufficient amount of time, the operpoint value will be restored to true.
A syslog message is issued when multiple source addresses are detected:
Receive Event: Multiple BPDU sources received on Port = ge.1.1 BPDU Source MAC = 00:00:00:01:02:03 Prior Source MAC = 00:00:00:0f:0e:0d
Note
When loop protect is configured for the port, if multisource detection is triggered, the port will go to the listening state and no longer be part of the active topology. Loop protect does not operate on shared media ports.
Print
this page
Email this topic
Feedback
View PDF
Download EPUB