Which command provides details about the serial interface controllers?

The command that provides details about the serial interface controllers is "show controllers." This command is specifically designed to display detailed information regarding the physical characteristics and status of the serial interfaces on a router. This includes information about the line cards, such as the number of serial interfaces, the state of the interfaces, and whether any line errors are occurring.

In contrast, while the "show interfaces" command may also provide some details about the interfaces, it focuses on a broader range of data, including both serial and other types of interfaces and their operational statuses rather than the specific hardware details of the controllers.

The "show serial" command does not exist as a standalone command in Cisco IOS. Instead, serial interfaces would be referenced through commands like "show interfaces."

The "show protocol" command primarily shows the state of Layer 3 protocols on the interfaces, which does not include detailed information about the physical controllers themselves. Each of these commands serves a different purpose in network management and diagnostics, but "show controllers" is the command that directly addresses the inquiry about serial interface controllers.