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FTOS Configuration Guide for the C-Series - Force10 Networks

FTOS Configuration Guide for the C-Series - Force10 Networks

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Preventing Network Disruptions with BPDU Guard<br />

The Portfast (and Edgeport, in <strong>the</strong> case of RSTP, PVST+, and MSTP) feature should be configured on<br />

ports that connect to end stations. End stations do not generate BPDUs, so ports configured with Portfast/<br />

Edgport (edgeports) do not expect to receive BDPUs. If an edgeport does receive a BPDU, it likely means<br />

that it is connected to ano<strong>the</strong>r part of <strong>the</strong> network, which can negatively effect <strong>the</strong> STP topology. The<br />

BPDU Guard feature blocks an edgeport upon receiving a BPDU to prevent network disruptions, and<br />

<strong>FTOS</strong> displays Message 22. Enable BPDU Guard using <strong>the</strong> option bpduguard when enabling PortFast or<br />

EdgePort.<br />

Figure 274 shows a scenario in which an edgeport might unintentionally receive a BPDU. The port on <strong>the</strong><br />

<strong>Force10</strong> system is configured with Portfast. If <strong>the</strong> switch is connected to <strong>the</strong> hub, <strong>the</strong> BPDUs that <strong>the</strong><br />

switch generates might trigger an undesirable topology change. If BPDU Guard is enabled, when <strong>the</strong> edge<br />

port receives <strong>the</strong> BPDU, <strong>the</strong> BPDU will be dropped, <strong>the</strong> port will be blocked, and a console message will<br />

be generated.<br />

Message 22 BPDU Guard Error<br />

3w3d0h: %RPM0-P:RP2 %SPANMGR-5-BPDU_GUARD_RX_ERROR: Received Spanning Tree BPDU on BPDU guard<br />

port. Disable GigabitE<strong>the</strong>rnet 3/41.<br />

Figure 274 Enabling BPDU Guard<br />

3/41<br />

Switch with Spanning Tree Enabled<br />

<strong>Force10</strong>(conf-if-gi-3/41)# spanning-tree 0 portfast bpduguard<br />

<strong>Force10</strong>(conf-if-gi-3/41)#show config<br />

!<br />

interface GigabitE<strong>the</strong>rnet 3/41<br />

no ip address<br />

switchport<br />

spanning-tree 0 portfast bpduguard<br />

no shutdown<br />

Hub<br />

fnC0064mp<br />

394 Spanning Tree Protocol

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