Reference Guide

Port enabled with loop guard conditions
• Loop guard is supported on any STP-enabled port or port-channel interface in RPVST+ mode.
• You cannot enable root guard and loop guard at the same time on an STP port — the loop guard conguration overwrites an existing
root guard conguration and vice versa.
• Enabling BPDU guard and loop guard at the same time on a port results in a port that remains in a Blocking state and prevents trac
from owing through it. For example, when you congure both Portfast BPDU guard and loop guard:
• If a BPDU is received from a remote device, BPDU guard places the port in an Err-Disabled Blocking state and no trac forwards
on the port.
• If no BPDU is received from a remote device which was sending BPDUs, loop guard places the port in a Loop-Inconsistent Blocking
state and no trac forwards on the port.
• When used in a PVST+ network, STP loop guard performs per-port or per port-channel at a VLAN level. If no BPDUs are received on a
port-channel interface, the port or port-channel transitions to a Loop-Inconsistent (Blocking) state only for this VLAN.
Global parameters
All non-root bridges accept the timer values on the root bridge.
Forward-time Amount of time required for an interface to transition from the Discarding to the Learning state or from the
Learning to the Forwarding state.
Hello-time Time interval within which the bridge sends BPDUs.
Max-age Length of time the bridge maintains conguration information before it refreshes information by recomputing the
RPVST+ topology.
• Modify the forward-time (in seconds) in CONFIGURATION mode (4 to 30, default 15).
spanning-tree vlan vlan-id forward-time seconds
• Modify the hello-time (in seconds) in CONFIGURATION mode (1 to 10, default 2). With large congurations (involving more number of
ports), Dell EMC recommends increasing the hello-time.
spanning-tree vlan vlan-id hello-time seconds
• Modify the max-age (in seconds) in CONFIGURATION mode (6 to 40, default 20).
spanning-tree vlan vlan-id max-age seconds
View RPVST+ global parameters
OS10# show spanning-tree active
Spanning tree enabled protocol rapid-pvst with force-version rstp
VLAN 1
Executing IEEE compatible Spanning Tree Protocol
Root ID Priority 32769, Address 90b1.1cf4.a523
Root Bridge hello time 2, max age 20, forward delay 15
Bridge ID Priority 32769, Address 90b1.1cf4.a523
We are the root of VLAN 1
Configured hello time 2, max age 20, forward delay 15
RPVST+ commands
clear spanning-tree counters
Clears the counters for STP.
Syntax
clear spanning-tree counters [interface {ethernet node/slot/port[:subport] |
port—channel number}}]
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