Reference Guide

Spanning Tree Protocol | 993
Figure 55-4. STP Root Guard Example
Root Guard Configuration
You enable STP root guard on a per-port or per-port-channel basis.
FTOS 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)
•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.
• Root guard and loop guard cannot be enabled at the same time on an STP port. When you configure root
guard on a port, an existing loop guard configuration is disabled.
• 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.