The error message %STP-2-DISPUTE_DETECTED could appear if a unidirectional link failure exists between two switches. A unidirectional link failure exists when a defective cable causes one device to not receive what the other device sends.

SwitchB cannot receive the superior bridge protocol data units (BPDUs) sent by SwitchA. Therefore, SwitchB will continue to send inferior BPDUs that are marked as designated and learning or forwarding. SwitchA will record the %STP-2-DISPUTE_DETECTED error and shut down the interface to prevent a bridging loop.

The error message %STP-2-DISPUTE_DETECTED would not appear if an interface has been administratively shut down. An interface that has been administratively shut down does not participate in Spanning Tree Protocol (STP).

The error message %STP-2-DISPUTE_DETECTED would not appear if a BPDU has been received on an interface with BPDU guard enabled; instead, the error message %STP-2-BLOCK_BPDUGUARD would appear. When an interface that is configured with BPDU guardreceives a BPDU, BPDU guard immediately puts the interface into the errdisable state and shuts down the interface. Afterward, the interface must be manually reenabled, or it can be recovered automatically through the errdisable timeout function.

The error message %STP2DISPUTE_DETECTED would not appear if a BPDU has not been received on an interface with Bridge Assurance enabled? instead, the error message %STP2-BRIDGE_ASSURANCE_BLOCK would appear. Bridge Assurance ensures that BPDUs are sent bidirectionally on all network interfaces. If an interface with Bridge Assurance does not receive a BPDU, or if the connected interface does not have Bridge
Assurance enabled, the interface is put into an inconsistent state and is blocked. Bridge Assurance is supported only with Rapid PerVLAN Spanning Tree Plus (RPVST +) and Multiple Spanning Tree (MST) and only on pointtopoint links.

The error message %STP-2-DISPUTE_DETECTED would not appear if an interface has received a BPDU that is tagged with the same virtual LAN (VLAN) ID as the interface's native VLAN? instead, the error message %STP-2-BLOCK_PVID_LOCAL would appear on the local switch and the error message %STP-2-BLOCK_PVID_PEER would appear on the remote switch. Native VLAN BPDUs are sent untagged, so if a switch receives BPDUs that are tagged with the native VLAN for that interface, the switch will block the interface.