Service Manual

Version Description
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 Introduced the loopguard and rootguard options on the E-Series, C-Series,
and S-Series.
8.3.7.0 Introduced on the S4810.
8.2.1.0 Introduced the hardware shutdown-on-violation option.
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.
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 the 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 a PVST switch, immediately transitions to the
forwarding state. Only ports connected to end-hosts should be configured as an edge port. 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 route process module
(RPM) CPU.
You cannot enable 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 is displayed: % Error: RootGuard is configured. Cannot configure
LoopGuard.
When used in a PVST+ network, loop guard is performed per-port or per-port channel at a VLAN level. If
no BPDUs are received on a VLAN interface, the port or port-channel transitions to a Loop-Inconsistent
(blocking) state only for this VLAN.
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-if-te-1/1)# spanning-tree pvst vlan 3 cost 1800
Dell(conf-if-te-1/1)# end
Dell(conf-if-te-1/1)# show config
!
interface TenGigabitEthernet 1/1
no ip address
switchport
spanning-tree pvst vlan 3 cost 1800
no shutdown
Dell(conf-if-te-1/1)# end
Dell#
Related
Commands
● show spanning-tree pvst — views the PVST+ configuration.
Per-VLAN Spanning Tree Plus (PVST+) 1121