Preventing Network Disruptions With Bpdu Guard - Dell Force10 S4810P Configuration Manual

To enable PortFast on an interface:
Task
Enable PortFast on an interface.
Verify that PortFast is enabled on a port using the
mode or the
show config
command, as shown in
config
Figure 49-3. PortFast Enabled on Interface
FTOS#(conf-if-gi-1/1)#show conf
!
interface GigabitEthernet 1/1
no ip address
switchport
spanning-tree 0 portfast
no shutdown
FTOS#(conf-if-gi-1/1)#

Preventing Network Disruptions with BPDU Guard

The Portfast (and Edgeport, in the case of RSTP, PVST+, and MSTP) feature should be configured 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 upon receiving a BPDU to prevent network disruptions, and
FTOS displays Message
EdgePort. The
bpduguard shutdown-on-violation
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
Figure 49-4 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 BPDU Guard is enabled, when the edge
port receives the BPDU, the BPDU will be dropped, the port will be blocked, and a console message will
be generated.
Message 1 BPDU Guard Error
3w3d0h: %RPM0-P:RP2 %SPANMGR-5-BPDU_GUARD_RX_ERROR: Received Spanning Tree BPDU on
BPDU guard port. Disable GigabitEthernet 3/41.
Command Syntax
spanning-tree stp-id portfast
[
shutdown-on-violation
command from INTERFACE mode; Dell Force10 recommends using the
Figure 49-3.
Indicates that the interface is in PortFast mode
1. Enable BPDU Guard using the option
option causes the interface hardware to be shutdown when it
[
bpduguard |
]]
command from the EXEC privilege
show spanning-tree
bpduguard
Command Mode
INTERFACE
show
when enabling PortFast or
after a BPDU violation.
packets
Spanning Tree Protocol (STP) | 1011