• Spanning Tree Protocol (STP)• Rapid Spanning Tree Protocol (RSTP)• Multiple Spanning Tree Protocol (MSTP)• Per-VLAN Spanning Tree Plus (PVST+)• When enabled on a port, root guard applies to all VLANs configured on the port.• You cannot enable root guard and loop guard at the same time on an STP port. For example, if you configure root guard on a port onwhich loop guard is already configured, the following error message displays: • % Error: LoopGuard is configured.Cannot configure RootGuard.• When used in an MSTP network, if root guard blocks a boundary port in the CIST, the port is also blocked in all other MST instances.To enable the root guard on an STP-enabled port or port-channel interface in instance 0, use the following command.• Enable root guard on a port or port-channel interface.INTERFACE mode or INTERFACE PORT-CHANNEL modespanning-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 interfaceconfiguration mode.To verify the STP root guard configuration on a port or port-channel interface, use the show spanning-tree 0 guard[interface interface] command in a global configuration mode.Enabling SNMP Traps for Root Elections and TopologyChangesTo 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 xstpConfiguring Spanning Trees as HitlessYou can configure STP, RSTP, MSTP, and PVST+ to be hitless (configure all or none as hitless). When configured as hitless, critical protocolstate 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.• Configure LACP to be hitless.CONFIGURATION moderedundancy protocol lacp• Configure all spanning tree types to be hitless.CONFIGURATION moderedundancy protocol xstpSpanning Tree Protocol (STP) 875
