Ann, a technician, connects a pair of switches using redundant links. When she checks the status of the links,
one of them is not active, even when she changes ports. Which of the following MOST likely disabled the
redundant connection to the other switch?

A.
Spanning tree

B.
IGRP routing

C.
SSID mismatch

D.
Port mirroring

Explanation:
http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/5234-5.html