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only implement bpduguard, although the interface is placed in an Error Disabled state when receiving
the BPDU, the physical interface remains up and spanning-tree drops packets in the hardware after a
BPDU violation. BPDUs are dropped in the software after receiving the BPDU violation.
CAUTION: Enable PortFast only on links connecting to an end station. PortFast can cause loops if
it is enabled on an interface connected to a network.
To enable PortFast on an interface, use the following command.
• Enable PortFast on an interface.
INTERFACE mode
spanning-tree stp-id portfast [bpduguard | [shutdown-on-violation]]
Example of Verifying PortFast is Enabled on an Interface
To verify that PortFast is enabled on a port, use the show spanning-tree command from EXEC
Privilege mode or the show config command from INTERFACE mode. Dell Networking recommends
using the
show config command.
Dell#(conf-if-te-1/1)#show conf
!
interface TenGigabitEthernet 1/1
no ip address
switchport
spanning-tree 0 portfast
no shutdown
Dell#(conf-if-te-1/1)#
Preventing Network Disruptions with BPDU Guard
Configure the Portfast (and Edgeport, in the case of RSTP, PVST+, and MSTP) feature on ports that
connect to end stations. End stations do not generate BPDUs, so ports configured with Portfast/ Edgport
(edgeports) do not expect to receive BDPUs.
If an edgeport does receive a BPDU, it likely means that it is connected to another part of the network,
which can negatively affect the STP topology. The BPDU Guard feature blocks an edgeport after
receiving a BPDU to prevent network disruptions, and the system displays the following message.
3w3d0h: %SYSTEM-P:RP2 %SPANMGR-5-BPDU_GUARD_RX_ERROR: Received Spanning Tree
BPDU on
BPDU guard port. Disable TenGigabitEthernet 3/41.
Enable BPDU Guard using the bpduguard option when enabling PortFast or EdgePort. The bpduguard
shutdown-on-violation
option causes the interface hardware to be shut down when it receives a
BPDU. Otherwise, although the interface is placed in an Error Disabled state when receiving the BPDU,
the physical interface remains up and spanning-tree will only drop packets after a BPDU violation.
The following example shows a scenario in which an edgeport might unintentionally receive a BPDU. The
port on the Dell Networking system is configured with Portfast. If the switch is connected to the hub, the
BPDUs that the switch generates might trigger an undesirable topology change. If you enable BPDU
Guard, when the edge port receives the BPDU, the BPDU is dropped, the port is blocked, and a console
message is generated.
NOTE: Unless you enable the shutdown-on-violation option, spanning-tree only drops packets
after a BPDU violation; the physical interface remains up.
Dell Networking OS Behavior: Regarding bpduguard shutdown-on-violation behavior:
876
Spanning Tree Protocol (STP)