Which of the following is typically used to manage a Cisco router in-band? (Select the best answer.)

A.
a VTY port

B.
a serial port

C.
a console port

D.
an auxiliary port

Explanation:
A virtual terminal (VTY) port is typically used to manage a Cisco router in-band. When a Cisco device is
operating in its normal state, another device can connect to it by using VTY application protocols such as Telnet
or Secure Shell (SSH). The use of VTY lines typically allows multiple administrators or management
applications to concurrently access a device from more than one location.
You would not use a console port or an auxiliary (AUX) port to manage a Cisco router in-band. You are most
likely to use either an AUX port or a console port to manage a Cisco router out-of-band, such as when the
router is in read-only memory (ROM) monitor (ROMmon) mode. The AUX port on a Cisco router is typically
capable of supporting most of the features available on a console port. Cisco switches either do not have AUX
ports or do not support certain features, such as system recovery, on their AUX ports if they have them.ROMmon is a management mode that Cisco routers and switches revert to when the system cannot find a
software image, the software image is corrupted, or the configuration register has been set to manually enter
ROMmon mode. Because ROMmon is an out-of-band management method, it can be used to recover system
software images, passwords, or other configuration data even when the router or switch is in a state where it
can no longer forward packets.
You would not use a serial port to manage a Cisco router in-band. Serial ports and Ethernet ports are used to
directly connect Cisco routers to other network devices. For example, you might use a serial port to directly
connect a Cisco router to other data terminal equipment (DTE) or data circuit-terminating equipment (DCE)
devices. You would also use a serial port to connect a router to a Channel Service Unit/Data Service Unit (CSU/
DSU).

Cisco: Cisco Guide to Harden Cisco IOS Devices: Management Interface Use