Administrator Guide

Version Description
6.2.1.1 Introduced on the E-Series.
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.
On the port extender (PE) ports and on VP-LAGs (LAGs created with PE):
● Spanning-tree with BPDU guard shutdown-on-violation is enabled as a default setting.
● No spanning tree command is valid. This command is not visible and issuing this command on VP-LAG
ports results in a failure.
Example
Dell(conf)#interface tengigabitethernet 2/0
Dell(conf-if-te-2/0)#spanning-tree rstp edge-port
Dell(conf-if-te-2/0)#show config
!
interface TenGigabitEthernet 2/0
no ip address
switchport
spanning-tree rstp edge-port
no shutdown
Dell#
tc-flush-standard
Enable the MAC address flushing after receiving every topology change notification.
C9000 Series
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, refer to the relevant Dell
Networking OS Command Line Reference Guide.
The following is a list of the Dell Networking OS version history for this command.
Rapid Spanning Tree Protocol (RSTP) 1465