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Figure 117. STP Root Guard Prevents Bridging Loops
Configuring Root Guard
Enable 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.
• 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 you
configure root guard on a port on which 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.
880
Spanning Tree Protocol (STP)