Dell Force10 MXL Blade MXL 10/40GbE Switch IO Module Configuration Guide - Page 587
Preventing Network Disruptions with BPDU Guard,
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To enable PortFast on an interface, use the following command: Task Enable PortFast on an interface. Command Syntax spanning-tree stp-id portfast [bpduguard [shutdown-on-violation] | bpdufilter] Command Mode 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 Force10 recommends using the show config command (Figure 33-7). 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)# Indicates that the interface is in PortFast mode 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. 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. Spanning Tree Protocol (STP) | 585
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