Chapter 2. Message and Recovery Procedures 35
SPANTREE-2-ROOTGUARD_BLOCK: Root guard blocking port [chars] on [chars].
Explanation This message means that on the listed interface a BPDU was received that advertises a
superior spanning-tree root bridge (lower bridge ID, lower path cost, and so forth) than that in use. The
interface is put into blocking state and marked as root-guard inconsistent to prevent a suboptimal
spanning-tree topology from forming. The first [chars] is the name of this port, and the second [chars] is
the spanning-tree instance on which this por t was blocked.
Response Enter the show spanning-tree inconsistentports privileged EXEC command to review the
list of interfaces with root-guard inconsistencies. Determine why devices connected to the listed ports are
sending BPDUs with a superior root bridge, and take action to prevent more occurrences. When the
inaccurate BPDUs have been stopped, the interfaces automatically recover and resume normal operation.
Make sure that it is appropriate to have root guard enabled on the interface.
SPANTREE-2-ROOTGUARD_CONFIG_CHANGE: Root guard [chars] on port [chars] on [chars].
Explanation This message means that the spanning-tree root guard configuration for the listed interface
has changed. If enabled, any BPDU received on this interface that advertises a superior spanning-tree
root bridge (lower bridge ID, lower path cost, and so forth) to that already in use causes the interface to
be put into the blocking state and marked as root-guard inconsistent. The first [chars] is the root-guard
state (enable or disable), the second [chars] is the interface, and the third [chars] is the spanning-tree
instance.
Response Verify that this is the desired configuration for the listed interface. Correct it if it is not the
desired configuration; otherwise, no action is required.
SPANTREE-2-ROOTGUARD_UNBLOCK: Root guard unblocking port [chars] on [chars].
Explanation This message means that the listed interface is no longer receiving BPDUs advertising a
superior root bridge (lower bridge ID, lower path cost, and so forth). The root-guard inconsistency is
cleared for the interface, and the blocking state is removed from th e interf ace. The first [ chars] is the name
of this port, and the second [chars] is the spanning-tree instance on which this port was blocked.
Response No action is required.
SPANTREE-2-UNBLOCK-CONSIST-PORT: Unblocking [chars] on [chars]. Port consistency restored.
Explanation This message means that the port VLAN ID or port type inconsistencies have been
resolved and that spanning tree will unblock the listed interface of the listed spanning-tree instance as
appropriate. The first [chars] is the interface, and the second [chars] is the spanning-tree instance.
Response No action is required.
SPANTREE-3-BAD_PORTNUM_SIZE: Rejected an attempt to se t the port number field s ize to [dec] bits (valid range
is [dec] to [dec] bits).
Explanation This message means that 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. That 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 increased to support the number of ports.