Administrator Guide

If you enable a root guard on all STP ports on the links where the root bridge should not appear, you can
ensure a stable STP network topology and avoid bridging loops.
Figure 115. 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.
Spanning Tree Protocol (STP) 883