To avoid loops at the data link layer, what should you configure in a network?

To avoid loops at the data link layer, configuring Spanning Tree Protocol (STP) is essential. STP is a network protocol that ensures a loop-free topology for computer networks. It works by identifying all the possible paths between network switches and then selectively blocking some of those paths to prevent circular traffic patterns that can lead to broadcast storms, multiple frame copies, and network congestion.

When STP is implemented, it dynamically determines the best active paths for data transmission while disabling redundant paths, which helps maintain a stable network environment. This is particularly crucial in environments with redundant links, where the risk of loops increases significantly. By intelligently managing the data paths, STP allows for efficient use of the available bandwidth while ensuring that data packets are not caught in endless loops.

In contrast, the other options do not specifically address the problem of loop prevention in the same manner. Port Mirroring is primarily used for monitoring and analyzing traffic, Link Aggregation groups multiple network connections to increase throughput and redundancy but does not inherently prevent loops, and EtherChannel, while similar to Link Aggregation, aggregates links for improved bandwidth without actively managing loop prevention through topology control as STP does.