Best Practice Recommendation for Spanning Tree Configuration in a vPC Environment
Question
Which option is the best practice recommendation for Spanning Tree configuration in a vPC environment?
Answers
Explanations
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A. B. C. D.Explanation.
In a vPC (virtual Port-Channel) environment, it is essential to ensure that Spanning Tree Protocol (STP) is configured correctly to avoid any loops or inconsistencies in the network. The best practice recommendation for Spanning Tree configuration in a vPC environment is to disable the Bridge Assurance feature on vPC links. This option is represented by answer D.
Bridge Assurance is a feature introduced in Rapid Spanning Tree Protocol (RSTP) to detect and prevent the occurrence of bridging loops. It operates by checking for the existence of BPDUs (Bridge Protocol Data Units) on all designated ports, including blocked ports. When a designated port fails to receive BPDUs from its connected neighbor, it assumes that a loop has occurred and transitions the port to the blocking state.
In a vPC environment, the Bridge Assurance feature can cause connectivity issues between vPC peers. The vPC peer-link is a special port-channel that is used to synchronize the MAC address tables of the vPC peer devices. When the Bridge Assurance feature is enabled on vPC links, it can cause unnecessary flapping of the vPC peer-link, leading to instability in the network.
Therefore, the best practice recommendation is to disable the Bridge Assurance feature on vPC links. This can be achieved by using the "no spanning-tree bridge assurance" command on the vPC peer-link interfaces. This configuration should be applied on both vPC peer devices to ensure consistency.
It is important to note that the other options provided in the answers are not the best practice recommendations for Spanning Tree configuration in a vPC environment. Disabling PortFast on host-facing interfaces (option A) can cause slow STP convergence, leading to longer network downtime in case of link failures. Disabling the BPDU Filter on the edge devices (option B) can lead to BPDU propagation, which can cause loops in the network. Disabling Rapid PVST or MST on all switches in the Layer 2 domain (option C) can cause slow STP convergence, which can impact the network's overall performance.
