Figure 119. STP Root Guard Prevents Bridging LoopsConfiguring Root GuardEnable STP root guard on a per-port or per-port-channel basis.Dell Networking OS Behavior: The following conditions apply to a port enabled with STP root guard:• Root guard is supported on any STP-enabled port or port-channel interface except when used as astacking port.• Root guard is supported on a port in any Spanning Tree mode:– 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 youconfigure root guard on a port on which loop guard is already configured, the following errormessage 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 alsoblocked in all other MST instances.To enable the root guard on an STP-enabled port or port-channel interface in instance 0, use thefollowing command.878 Spanning Tree Protocol (STP)
