Command Line Reference Guide

Version Description
9.2(1.0) Introduced on the Z9500.
8.3.19.0 Introduced on the S4820T.
8.3.11.1 Introduced on the Z9000.
8.4.2.1 Added support for the optional guard keyword on the C-
Series, S-Series, and E-Series TeraScale.
8.3.7.0 Introduced on the S4810.
8.2.1.0 Introduced the hardware shutdown-on-violation
options.
7.6.1.0 Introduced on the S-Series.
7.5.1.0 Introduced on the C-Series.
7.4.1.0 Added the optional bridge port data unit (BPDU) guard.
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.
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
Rapid Spanning Tree Protocol (RSTP)
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