Final answer:
To prevent network slowdown caused by looping frames in a managed switch network, enabling Spanning Tree Protocol (STP) is the solution. STP creates a loop-free network topology, allowing only one active path and preventing broadcast storms.
Step-by-step explanation:
A solution to prevent network slowdown due to looping frames on a network with multiple managed switches is to enable Spanning Tree Protocol (STP). STP is a network protocol that creates a loop-free logical topology for ethernet networks. It prevents network loops by dynamically blocking redundant paths and only allowing a single active path between two network devices. When multiple paths exist, STP uses a root bridge election and a path cost calculation to determine which paths to enable for traffic, effectively stopping loops that can lead to broadcast storms and network slowdowns.