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Impact of loopguard removal

Hi,

We need to remove loopguard from some DC switches,

Is there any impact of this removal -

We do not expect any STP reconvergence - but would like confirmation

Loopguard caused an outage due to a known bug in some of our switches

Cheers

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VIP Mentor

Impact of loopguard removal

HI Dominic,

As per my knowledge it will not afftect the operation.

When implementing Loop Guard, you should be aware of the following implementation  guidelines;

  • Loop Guard cannot be enabled on a switch that also has Root Guard enabled
  • Loop Guard does not affect Uplink Fast or Backbone Fast operation
  • Loop Guard must be enabled on point-to-point links only
  • Loop Guard operation is not affected by the Spanning Tree timers
  • Loop Guard cannot actually detect a unidirectional link
  • Loop Guard cannot be enabled on Port Fast or Dynamic VLAN ports

You can use Loop Guard to determine if a root port or an alternate/backup root port receives BPDUs. If the port does not receive BPDUs, Loop Guard puts the port into an inconsistent state (blocking) until the port starts to receive BPDUs again. A port in the inconsistent state does not transmit BPDUs. If the port receives BPDUs again, the protocol removes its loop-inconsistent condition, and the STP determines the port state because such recovery is automatic.

Loop Guard isolates the failure and allows STP to converge to a stable topology without the failed link or bridge. Disabling Loop Guard moves all loop-inconsistent ports to the listening state.

Regards

Please rate if it helps.

View solution in original post

1 REPLY 1
VIP Mentor

Impact of loopguard removal

HI Dominic,

As per my knowledge it will not afftect the operation.

When implementing Loop Guard, you should be aware of the following implementation  guidelines;

  • Loop Guard cannot be enabled on a switch that also has Root Guard enabled
  • Loop Guard does not affect Uplink Fast or Backbone Fast operation
  • Loop Guard must be enabled on point-to-point links only
  • Loop Guard operation is not affected by the Spanning Tree timers
  • Loop Guard cannot actually detect a unidirectional link
  • Loop Guard cannot be enabled on Port Fast or Dynamic VLAN ports

You can use Loop Guard to determine if a root port or an alternate/backup root port receives BPDUs. If the port does not receive BPDUs, Loop Guard puts the port into an inconsistent state (blocking) until the port starts to receive BPDUs again. A port in the inconsistent state does not transmit BPDUs. If the port receives BPDUs again, the protocol removes its loop-inconsistent condition, and the STP determines the port state because such recovery is automatic.

Loop Guard isolates the failure and allows STP to converge to a stable topology without the failed link or bridge. Disabling Loop Guard moves all loop-inconsistent ports to the listening state.

Regards

Please rate if it helps.

View solution in original post

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