How to Ensure the Switch is Always the Root for VLAN 750

C

The correct answer to ensure that the switch is always the root for VLAN 750 is A. Switch(config)#spanning-tree vlan 750 priority 38418607.

Spanning Tree Protocol (STP) is a protocol that prevents network loops by disabling redundant links and blocking certain ports. STP builds a loop-free topology of the network by selecting one switch as the root of the spanning tree, and all other switches in the network choose their uplink port to reach the root switch.

The priority value is used in STP to determine the root switch. The switch with the lowest priority value is elected as the root switch for the particular VLAN. By default, all switches have the same priority value (32768), so if there are no other changes made, the switch with the lowest MAC address will be elected as the root switch for that VLAN.

To ensure that the switch is always the root for VLAN 750, we need to lower the priority value of the switch to a value lower than any other switches in the network for VLAN 750. The command to set the priority value for VLAN 750 is:

Switch(config)#spanning-tree vlan 750 priority <priority-value>

The priority value can be any value between 0 and 65535, with increments of 4096. The lower the priority value, the higher the priority of the switch.

Option B (Switch(config)#spanning-tree vlan 750 priority 0) sets the priority value to the lowest possible value, which is not recommended as it can cause network instability and loops.

Option C (Switch(config)#spanning-tree vlan 750 root primary) forces the switch to become the root switch for VLAN 750, but it is not a recommended configuration as it can cause issues if there is a switch with a lower priority in the network that may be better suited to be the root switch.

Option D (Switch(config)#spanning-tree vlan 750 priority 614440) sets the priority value to a value higher than the default value, which will not ensure that the switch is always the root for VLAN 750.

Therefore, the correct answer is A (Switch(config)#spanning-tree vlan 750 priority 38418607), which sets the priority value to a value lower than any other switches in the network for VLAN 750, ensuring that this switch will always be the root switch for that VLAN.