Concept Guide

spanning-tree {0 | mstp | rstp | pvst} rootguard
– 0: enables root guard on an STP-enabled port assigned to instance 0.
– mstp: enables root guard on an MSTP-enabled port.
– rstp: enables root guard on an RSTP-enabled port.
– pvst: enables root guard on a PVST-enabled port.
To disable STP root guard on a port or port-channel interface, use the no spanning-tree 0 rootguard command in an interface
conguration mode.
To verify the STP root guard conguration on a port or port-channel interface, use the show spanning-tree 0 guard
[interface interface] command in a global conguration mode.
Enabling SNMP Traps for Root Elections and Topology
Changes
To enable SNMP traps individually or collectively, use the following commands.
• Enable SNMP traps for spanning tree state changes.
snmp-server enable traps stp
• Enable SNMP traps for RSTP, MSTP, and PVST+ collectively.
snmp-server enable traps xstp
Conguring Spanning Trees as Hitless
You can congure STP, RSTP, MSTP, and PVST+ to be hitless (congure all or none as hitless). When congured as hitless, critical protocol
state information is synchronized between the RPMs so that RPM failover is seamless and no topology change is triggered.
To be hitless per spanning tree type or for all spanning tree types, use the following commands.
• Congure LACP to be hitless.
CONFIGURATION mode
redundancy protocol lacp
• Congure all spanning tree types to be hitless.
CONFIGURATION mode
redundancy protocol xstp
Example of Conguring all Spanning Tree Types to be Hitless
DellEMC(conf)#redundancy protocol xstp
DellEMC#show running-config redundancy
!
redundancy protocol xstp
DellEMC#
STP Loop Guard
The STP loop guard feature provides protection against Layer 2 forwarding loops (STP loops) caused by a hardware failure, such as a cable
failure or an interface fault. When a cable or interface fails, a participating STP link may become unidirectional (STP requires links to be
bidirectional) and an STP port does not receive BPDUs. When an STP blocking port does not receive BPDUs, it transitions to a Forwarding
state. This condition can create a loop in the network.
For example, in the following example (STP topology 1, upper left), Switch A is the root switch and Switch B normally transmits BPDUs to
Switch C. The link between Switch C and Switch B is in a Blocking state. However, if there is a unidirectional link failure (STP topology 1,
900
Spanning Tree Protocol (STP)