Understanding and Configuring SpanGuard
Fixed Switch Configuration Guide 15-29
Monitoring MSTP
Use the commands in Table 15-8 to monitor MSTP statistics and configurations on stackable, and
standalone switch devices. You can also use the show commands described in “Reviewing and
Enabling Spanning Tree” on page 15-20 to review information related to all Spanning Tree
protocol activity.
Understanding and Configuring SpanGuard
What Is SpanGuard?
As described previously in the overview of “SpanGuard” on page 15-7, this feature enables
Enterasys switching devices to detect unauthorized bridges in your network, resolving the threat
of repeated topology change notifications or new root bridge announcements causing a Denial of
Service (DoS) condition. It prevents Spanning Tree respans that can occur when BPDUs are
received on user ports and notifies you (network management) they were attempted.
If a SpanGuard enabled port receives a BPDU, it becomes locked and transitions to the blocking
state. It will only transition out of the blocking state after a globally specified time or when it is
manually unlocked.
By default, SpanGuard is globally disabled on stackable, and standalone switch devices and must
be globally enabled to operate on all user ports. For configuration information, refer to
“Configuring SpanGuard” on page 15-30.
Table 15-8 Commands for Monitoring MSTP
Task Command
Verify that MSTP is running on the device. show spantree version
Display a list of MSTIs configured on the device. show spantree mstilist
Display the mapping of one or more filtering
database IDs (FIDs) to Spanning Trees. Since
VLANs are mapped to FIDs, this shows to which SID
a VLAN is mapped.
show spantree mstmap [fid fid]
Display the Spanning Tree ID(s) assigned to one or
more VLANs.
show spantree vlanlist [vlan-list]
Display MST configuration identifier elements,
including format selector, configuration name,
revision level, and configuration digest.
show spantree mstcfgid
Display protocol-specific MSTP counter information. show spantree debug [port port-string]
[sid sid] [active]
For information about... Refer to page...
What Is SpanGuard? 15-29
How Does It Operate? 15-31
Configuring SpanGuard 15-30
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