What is the default speed setting of an interface?

The default speed setting of an interface on Cisco devices, such as routers and switches, is typically set to "auto." This means that the interface is configured to automatically negotiate the speed with the connected device, allowing it to adapt to the optimal speed based on the capabilities of both devices. This automatic negotiation simplifies the configuration process because network administrators do not need to manually set the speed, which can be particularly beneficial in environments with diverse equipment where devices may support different speeds.

The other choices represent specific speeds that interfaces may support, but under normal circumstances, the default configuration leverages the auto-negotiation feature to ensure that any connected device can establish the best possible connection without manual intervention. This flexibility is crucial in maintaining network performance and compatibility across various devices.