CompTIA Network+ Practice Test

Which protocol helps maintain a loop-free environment in switched networks?

1. Link Aggregation Control Protocol (LACP)

2. Spanning Tree Protocol (STP)

3. Virtual Router Redundancy Protocol (VRRP)

4. Dynamic Host Configuration Protocol (DHCP)

The correct answer is: Spanning Tree Protocol (STP)

The Spanning Tree Protocol (STP) is essential for maintaining a loop-free environment in switched networks. It operates at the data link layer (Layer 2) and is designed to prevent broadcast storms that can occur due to loops in a network. When multiple switches are interconnected, the presence of redundant paths can lead to loops, which can cause packets to circulate infinitely, resulting in network congestion and inefficient communication. STP works by first identifying all the switches in the network and then determining the best path to each switch, effectively blocking any redundant paths that could create loops. It does this by designating a root bridge and using algorithms to calculate the shortest paths while placing selected ports into a blocking state to prevent loops. While the other protocols mentioned serve their own important functions—such as link aggregation, router redundancy, and dynamic IP address assignment—they do not specifically address the issue of loops in switched networks. LACP manages the aggregation of multiple links into a single logical link to increase bandwidth and provide redundancy. VRRP provides high availability for IP addresses by enabling a backup router in case the primary fails, and DHCP is primarily concerned with assigning IP addresses dynamically to devices on a network. None of these directly tackle the problem of preventing loops in the network topology as