Reference Guide

Spanning Tree Protocol (STP) | 585
To enable PortFast on an interface, use the following command:
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 Force10 recommends using the show
config
command (Figure 33-7).
Figure 33-7. show config Command Example (PortFast Enabled)
Preventing Network Disruptions with BPDU Guard
You must 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 effect the STP topology. The
BPDU guard feature blocks an edgeport after receiving a BPDU to prevent network disruptions and FTOS
displays Message 1.
To enable BPDU guard, use the
bpduguard option when enabling PortFast or EdgePort. The bpduguard
shutdown-on-violation
option causes the interface hardware to be shutdown 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 STP only drops
packets after a BPDU violation.
Figure 33-8 shows a scenario in which an edgeport might unintentionally receive a BPDU. The port on the
Dell Force10 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 enabled BPDU guard, when the
edge port receives the BPDU, the BPDU is dropped, the port is blocked, and a console message is
generated.
Task Command Syntax Command Mode
Enable PortFast on an interface.
spanning-tree stp-id portfast [bpduguard
[shutdown-on-violation] | bpdufilter]
INTERFACE
Message 1 BPDU Guard Error
4d23h40m: %STKUNIT3-M:CP %SPANMGR-5-BPDU_GUARD_RX_ERROR: Received Spanning Tree BPDU on BPDU
guard port. Disable TenGigabitEthernet 3/20.
FTOS#(conf-if-te-1/1)#show conf
!
interface Tengigabitethernet 1/1
no ip address
switchport
spanning-tree 0 portfast
no shutdown
FTOS#(conf-if-te-1/1)#
Indicates that the interface is in PortFast mode