Preventing Network Disruptions With Bpdu Guard - Dell Force10 C150 Configuration Manual

To enable PortFast on an interface:
Task
Enable PortFast on an interface.
Verify that PortFast is enabled on a port using the
show config
mode or the
config
command, as shown in
Figure 52-7. 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 BPDUs. If an edge port 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 edge port upon receiving a BPDU to prevent network disruptions, and
FTOS displays Message
Caution:
Do not enable Portfast BPDU guard and loop guard at the same time on a port. Enabling both features
may result 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.
Enable BPDU Guard using the option
bpduguard shutdown-on-violation
BPDU. Otherwise with only the option enabled, 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
after a BPDU violation.
Command Syntax
spanning-tree stp-id portfast
bpduguard shutdown-on-violation
[ [
command from INTERFACE mode; Dell Force10 recommends using the
Figure 52-7.
Indicates that the interface is in PortFast mode
1.
bpduguard
option to cause the interface hardware to shut down when it receives a
]]
show spanning-tree
command from the EXEC privilege
when enabling PortFast or EdgePort. Configure the
Command Mode
INTERFACE
show
packets
Spanning Tree Protocol | 1057