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Catalyst 3750, 3560, 3550, 2975, 2970, and 2960 Switch System Message Guide
OL-8551-04
Chapter 3 Message and Recovery Proced ures
SPANTREE Messages
Error Message SPANTREE-3-BAD_PORTNUM_SIZE: Rejected an attempt to set the port
number field size to [dec] bits (valid range is [dec] to [dec] bits).
Explanation An error occurred in the platform-specific code that caused it to request more or less
bits than are possible. The spanning-tree port identifier is a 16-bit field, which is divided evenly
between the port priority and port number, with each subfield being 8 bits. This allows the port
number field to represent port numbers between 1 and 255. However, on systems with more than
255 ports, the size of port number portion of the port ID must be in creased to support the number of
ports. This is performed by the spanning-tree subsystem at system initialization because the
maximum number of ports on a particular platform will not change. This error occurs because of an
error in the platform-specific code, which causes it to request more or less bits than are possible.
The first [dec] is the number of bits for the port number, and the second and third [dec] describe the
valid range.
Recommended Action Copy the message exactly as it appears on the console or in the system log.
Research and attempt to resolve the error by using the Output Interpreter. Enter the show version
user EXEC command to gather data that might help identify the nature of the error. Use the Bug
Toolkit to look for similar reported problems. If you still require assistance, open a case with the
TAC, or contact your Cisco technical support representative, and provide the representative with the
gathered info rmation. For more information about these online tools and about contacting Cisco, see the
“Error Message Traceback Reports” section on page 2-7.
Error Message SPANTREE-3-PORT_SELF_LOOPED: [chars] disabled.- received BPDU src mac
([enet]) same as that of interface.
Explanation A BPDU was received on the listed interface with a source MAC address that matches
the one assigned to the listed interface. This means that a port might be looped back to itself,
possibly because of an installed diagnostic cable. The interface will be administratively shut down.
[chars] is the interface that received the BPDU, and [enet] is the source MAC address.
Recommended Action Check the interface configuration and any cable connected to the interface.
When the problem is resolved, re-enable the interface by entering the no shutdown interface
configuration command.
Error Message SPANTREE-3-PRESTD_NEIGH: pre-standard MST interaction not configured
([chars]).
Explanation The message means that the switch has received a prestandard multiple spanning-tree
(MST) BPDU on an interface that is not configured to send prestandard MST BPDUs. The switch
automatically adjusts its configuration on the interface and start sending prestandard BPDUs.
However, the switch does not automatically detect all prestandard neighbors, and we recommend
that you configure the interface to send prestandard MST BPDUs by usi ng the spanning-tree mst
pre-standard interface configuration command. This warning message only appears once. [chars]
is the interface.
Recommended Action Use the spanning-tree mst pre-standard interface configuration command on
all the interfaces to which other switches running Cisco's prestandard MST version are connected.
We recommend that you migrate all the switches in the network to the IEEE MST standard version.