Which result occurs when PortFast is enabled on an interface that is connected to another switch?
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A. B. C. D.D.
Enabling the PortFast feature causes a switch or a trunk port to enter the STP forwarding-state immediately or upon a linkup event, thus bypassing the listening and learning states.
Note: To enable portfast on a trunk port you need the trunk keyword spanning-tree portfast trunk.
PortFast is a Cisco feature that is used to enable a switch port to immediately transition from the blocking state to the forwarding state, bypassing the listening and learning states. This feature is typically used on ports that are connected to end-user devices such as workstations, printers, and servers.
When PortFast is enabled on an interface that is connected to another switch, it can cause a switching loop in the network. This is because the switch connected to the PortFast-enabled interface will immediately transition to the forwarding state, without going through the normal listening and learning states. If there is a loop in the network, this can cause broadcast storms and other issues.
Option D is therefore the correct answer. Enabling PortFast on an interface that is connected to another switch can cause spanning-tree to fail to detect a switching loop in the network, which can lead to broadcast storms and other issues.
Option A is incorrect because PortFast does not affect the root port choice or the spanning-tree recalculation process.
Option B is incorrect because PortFast does not shut down any port that receives BPDUs. Instead, it ignores the BPDUs and immediately transitions the port to the forwarding state.
Option C is also incorrect because VTP (VLAN Trunking Protocol) is not related to PortFast. VTP is used to propagate VLAN configuration information between switches in a network.