Preventing Network Disruptions With Bpdu Guard - Dell Force10 MXL Blade Configuration Manual

To enable PortFast on an interface, use the following command:
Task
Enable PortFast on an interface.
To verify that PortFast is enabled on a port, use the
mode or the
show config
command
config
Figure 33-7. show config Command Example (PortFast Enabled)
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)#

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
To enable BPDU guard, use the
shutdown-on-violation
Otherwise, although the interface is placed in an Error Disabled state when receiving the BPDU, the
physical interface remains up and STP only drops
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.
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.
Command Syntax
spanning-tree stp-id portfast [bpduguard
[shutdown-on-violation] | bpdufilter]
command from INTERFACE mode. Dell Force10 recommends using the
(Figure 33-7).
1.
bpduguard
option causes the interface hardware to be shutdown when it receives a BPDU.
show spanning-tree
Indicates that the interface is in PortFast mode
option when enabling PortFast or EdgePort. The
after a BPDU violation.
packets
Command Mode
INTERFACE
command from EXEC privilege
bpduguard
Spanning Tree Protocol (STP) | 585
show