Users Guide

Debug congurations
Use the debug spanning-tree bpdu command to monitor and verify that the MST conguration is communicating as congured. 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 conguration, or use the show running-configuration
command to view the overall MST conguration.
MST ags 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
Dierent Region, one of the key parameters does not match.
MST region name
and revision
The congured name and revisions must be identical among all devices. If the region name is blank, a name was
congured on one device and was not congured or was congured dierently 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 congured 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 conguration
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 specied in IEEE 802.1w, OS10 assumes a port that runs in full-duplex mode as 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.
As the half-duplex mode is considered as a shared link, the fast transition feature is not applicable for shared links. If you 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
Common STP commands
Layer 2
399