Users Guide

RPVST allows (VLAN, port) based flush until the number of calls sent is equal to the MAC flush threshold value that is configured.
When the number of calls sent exceeds the configured threshold, RPVST ignores further (VLAN, port) based flush and starts the MAC
flush timer. When the timer starts, the system blocks further flush. When the timer expires for that specific instance, the system triggers
VLAN-based flushing.
By default, the MAC flush threshold value is set to 5. However, Dell EMC recommends that you configure this value based on the number
of ports that participate in the STP topology.
Debug configurations
Use the debug spanning-tree bpdu command to monitor and verify that the MST configuration is communicating as configured.
To ensure all necessary parameters match — region name, region version, and VLAN to instance mapping, examine your individual
devices. Use the
show spanning-tree mst command to view the MST configuration, or use the show running-
configuration command to view the overall MST configuration.
MST flags for
communication
received from the
same region
The MST routers are located in the same region. If the debug logs indicate that packets are coming from a
Different Region, one of the key parameters does not match.
MST region name
and revision
The configured name and revisions must be identical among all devices. If the region name is blank, a name was
configured on one device and was not configured or was configured differently on another — spelling and
capitalization count.
MST instances Verify the VLAN-to-MST instance mapping using the show commands. If you see extra MST instances in the
Sending or Received logs, an additional MST instance was configured on one router but not the others.
• View BPDUs in EXEC mode.
debug spanning-tree bpdu
• View MST-triggered topology change messages in EXEC mode.
debug spanning-tree events
View MST configuration
OS10# show spanning-tree mst configuration
Region Name: force10
Revision: 100
MSTI VID
0 1,31-4093
1 2-10
2 11-20
3 21-30
Setting spanning-tree link type for rapid state transitions
As specified in IEEE 802.1w, OS10 assumes a port that runs in full-duplex mode is a point-to-point link. A point-to-point link transitions to
forwarding state faster. By default, OS10 derives the link type of a port from the duplex mode. You can override the duplex mode using
the
spanning-tree link-type command.
OS10 assumes a port that runs in half-duplex mode is a shared link, to which the fast transition feature is not applicable. Also, If you
explicitly designate a port as a shared link, you cannot use the fast transition feature, regardless of the duplex setting.
To hasten the spanning-tree state transitions, you can set the link type to point-to-point. To set the link type to point-to-point:
• Use the following command in INTERFACE mode.
spanning-tree link-type point-to-point
422
Layer 2