Exam 200-301 topic 1 question 246 discussion

there is the same question earlier this one, but taht answer is D ...

set as Primary dose not grantee the root stay as root always. set as zero grantees the root will always be root.

The correct answer is C (spanning-tree vlan 200 root primary) and not B (priority 0): While configuring spanning-tree vlan 200 priority 0 (option B) sets the lowest possible STP priority value, it is a manual and static configuration. It does not dynamically evaluate the current root bridge in the topology and does not adapt if changes occur later in the network. In contrast, spanning-tree vlan 200 root primary (option C) is the Cisco-recommended and dynamic method to ensure a switch becomes — and stays — the root bridge for a given VLAN. This command: Automatically sets the switch’s priority to 24576, or If another switch already has a lower priority, it will set the local priority to 4096 less than the current root’s priority This ensures the local switch takes over as the root bridge without the need for manual priority calculation and provides greater flexibility and reliability in real-world environments. Correct Answer: C

The primary keyword sets the priority to 24,576, and the secondary keyword sets the priority to 28,672. spanning-tree vlan vlan-id root {primary | secondary} [diameter diameter]: This command executes a script that modifies certain values. Explanation in this link. https://www.ciscopress.com/articles/article.asp?p=2995351&seqNum=2

I think C is correct. When you connect another switch with the same priority 0, won't a root bridge election take place? And since an election happens, there's no guarantee that the switch will be the root since the other switch may have a lower MAC address.

In Rapid PVST+ (Per-VLAN Spanning Tree Plus) protocol, you can use the "spanning-tree vlan 200 root primary" command to ensure that a switch becomes the root bridge for VLAN 200. This command sets the priority of the switch to the lowest value (0) for the specified VLAN, making it the root bridge. By setting the priority to the lowest value, the switch will have the highest priority and will become the root bridge for the specified VLAN. Keep in mind that this command only affects VLAN 200 and does not impact the spanning tree topology for other VLANs. Here's the complete command: Copy switch(config)# spanning-tree vlan 200 root primary Make sure to execute this command on the desired switch to ensure it becomes the root bridge for VLAN 200 in Rapid PVST+ topology.

last question i came across with setting the priority to zero(0) was incorrect and now its correct lol... i think we need to follow our books more in as much as we need to revise

About root primary command: https://community.cisco.com/t5/switching/spanning-tree-vlan-root-primary/td-p/1269595 Paraphrasing from this source: The "spanning-tree root primary" command is actually a macro and it is executed only one time. If after this somebody configures another device with a lower priority, this node cannot react to this and it will lose its root bridge role. If you use "spanning-tree vlan 1 priority 0", only another device with pri 0 and a lower MAC address can take the role of root bridge.

C. spanning-tree vlan 200 root primary

The spanning-tree vlan vlan_ID root command fails if the value required to be the root bridge is less than 1. https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/layer2/503_n1_1/Cisco_n5k_layer2_config_gd_rel_503_N1_1_chapter9.html#task_1163819

The spanning-tree vlan vlan_ID root command fails if the value required to be the root bridge is less than 1. https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/layer2/503_n1_1/Cisco_n5k_layer2_config_gd_rel_503_N1_1_chapter9.html

B is correct!

Correct Answer C technically B is relevant only if you want to change the priority of the root bridge, but to ensure the switch is always the root bridge you must explicitly configure it as the root eg SW4(config)#spanning-tree vlan 1 ? priority Set the bridge priority for the spanning tree root Configure switch as root <cr> https://www.omnisecu.com/cisco-certified-network-associate-ccna/how-to-configure-spanning-tree-protocol-root-primary-and-root-secondary.php

The key phrase "guaranteed is always". using the primary command causes the switch to check the existing root switch priority and then lower its priority by 4096. This is only done once thus if a new switch is introduced later with an even lower priority that switch will become root bridge. The only way to guarantee a switch remains root is to set its priority to 0.

thank you is there a new qoustions about ccna 2021 after changing exam rules

I looked at other resouces because I though the answer was C, but B seems to be correct

B true