Cisco Nexus 6000, Руководство по настройке

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BPDU Filtering State STP Edge Port
Configuration BPDU Filtering Global
Configuration BPDU Filtering Per Port
Configuration
Disabled Disabled Enabled Default
Disabled Enabled/Disabled Disabled Default
Disabled Enabled/Disabled Enabled/Disabled Disable
Enabled
BPDUs are
never sent and
if received,
they do not
trigger the
regular STP
behavior - use
with caution.
Caution
Enabled/Disabled Enabled/Disabled Enabled
Understanding Loop Guard
Loop Guard protects networks from loops that are caused by the following:
• Network interfaces that malfunction
• Busy CPUs
• Anything that prevents the normal forwarding of BPDUs
An STP loop occurs when a blocking port in a redundant topology erroneously transitions to the forwarding
state. This transition usually happens because one of the ports in a physically redundant topology (not
necessarily the blocking port) stops receiving BPDUs.
Loop Guard is useful only in switched networks where devices are connected by point-to-point links. On a
point-to-point link, a designated bridge cannot disappear unless it sends an inferior BPDU or brings the link
down.
Loop Guard can be enabled only on network and normal spanning tree port types.
Note
You can use Loop Guard to determine if a root port or an alternate/backup root port receives BPDUs. If the
port does not receive BPDUs, Loop Guard puts the port into an inconsistent state (blocking) until the port
starts to receive BPDUs again. A port in the inconsistent state does not transmit BPDUs. If the port receives
BPDUs again, the protocol removes its loop-inconsistent condition, and the STP determines the port state
because such recovery is automatic.
Loop Guard isolates the failure and allows STP to converge to a stable topology without the failed link or
bridge. Disabling Loop Guard moves all loop-inconsistent ports to the listening state.
You can enable Loop Guard on a per-port basis. When you enable Loop Guard on a port, it is automatically
applied to all of the active instances or VLANs to which that port belongs. When you disable Loop Guard, it
is disabled for the specified ports.
Cisco Nexus 6000 Series NX-OS Layer 2 Switching Configuration Guide, Release 7.x
96
Configuring STP Extensions
Information About STP Extensions