Administrator Guide

Usage Information
The BPDU guard option prevents the port from participating in an active STP topology in case a BPDU appears
on a port unintentionally, or is misconfigured, or is subject to a DOS attack. This option places the port into an
Error Disable state if a BPDU appears and a message is logged so that the administrator can take corrective
action.
NOTE: A port configured as an edge port, on an RSTP switch, immediately transitions to the
Forwarding state. Only configure ports connected to end-hosts as edge ports. Consider an edge
port similar to a port with a spanning-tree portfast enabled.
If you do not enable shutdown-on-violation, BPDUs are still sent to the RPM CPU.
You cannot enable STP root guard and loop guard at the same time on a port. For example, if you configure loop
guard on a port on which root guard is already configured, the following error message displays: % Error:
RootGuard is configured. Cannot configure LoopGuard.
Enabling Portfast BPDU guard and loop guard at the same time on a port results in a port that remains in a
Blocking state and prevents traffic from flowing through it. For example, when Portfast BPDU guard and loop
guard are both configured:
• If a BPDU is received from a remote device, BPDU guard places the port in an Err-Disabled Blocking state and
no traffic is forwarded on the port.
• If no BPDU is received from a remote device, loop guard places the port in a Loop-Inconsistent Blocking state
and no traffic is forwarded on the port.
Example
DellEMC(conf)# interface tengigabitethernet 4/1
DellEMC(conf-if-gi-4/0)# spanning-tree rstp edge-port
DellEMC(conf-if-gi-4/0)# show config
!
interface TenGigabitEthernet 4/1
no ip address
switchport
spanning-tree rstp edge-port
no shutdown
DellEMC#
tc-flush-standard
Enable the MAC address flushing after receiving every topology change notification.
Syntax
tc-flush-standard
To disable, use the no tc-flush-standard command.
Defaults Disabled
Command Modes CONFIGURATION (conf-rstp)
Command History
This guide is platform-specific. For command information about other platforms, see the relevant Dell EMC
Networking OS Command Line Reference Guide.
Version Description
9.10(0.1) Introduced on the S6010-ON and S4048T-ON.
9.10(0.0) Introduced on the S3148.
9.10(0.0) Introduced on the S6100-ON.
9.8(2.0) Introduced on the S3100 series.
9.8(1.0) Introduced on the Z9100-ON.
9.8(0.0P5) Introduced on the S4048-ON.
9.8(0.0P2) Introduced on the S3048-ON.
9.7(0.0) Introduced on the S6000-ON.
9.2(1.0) Introduced on the Z9500.
Rapid Spanning Tree Protocol (RSTP) 1367