Configuration manual

Enabling PortFast
The PortFast feature enables interfaces to begin forwarding traffic approximately 30 seconds sooner.
Interfaces forward frames by default until they receive a BPDU that indicates that they should behave
otherwise; they do not go through the Learning and Listening states. The
bpduguard shutdown-on-
violation option causes the interface hardware to be shut down when it receives a BPDU. When you
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.
PDU Filtering enabled on an interface stops sending and receiving BPDUs on the port fast enabled ports.
When you enable BPDU guard and BPDU filter on the port, then BPDU filter takes the highest
precedence. By default BPDU filtering on an interface is disabled.
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] |
bpdufilter]
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)#
Prevent 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: %RPM0-P:RP2 %SPANMGR-5-BPDU_GUARD_RX_ERROR: Received Spanning Tree BPDU
on
BPDU guard port. Disable GigabitEthernet 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
Spanning Tree Protocol (STP)
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