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Figure 123. 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 except when used as a stacking port.
Root guard is supported on a port in any Spanning Tree mode:
Spanning Tree Protocol (STP)
Rapid Spanning Tree Protocol (RSTP)
Multicast Source Discovery Protocol (MSDP)
Per-VLAN Spanning Tree Plus (PVST+)
When enabled on a port, root guard applies to all VLANs configured on the port.
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 mode
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 configuration 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.
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Spanning Tree Protocol (STP)