Users Guide

Version Description
9.2(1.0) Introduced on the Z9500.
9.0.2.0 Introduced on the S6000.
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.
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 4/1
Dell(conf-if-gi-4/0)# spanning-tree rstp edge-port
Dell(conf-if-gi-4/0)# show config
!
interface TenGigabitEthernet 4/1
no ip address
switchport
spanning-tree rstp edge-port
no shutdown
Dell#
Rapid Spanning Tree Protocol (RSTP) 1402