Two switches are connected together using two crossover cables to provide redundancy, but Spanning Tree Protocol (STP) is disabled on both switches. In this situation, what is the most likely effect on the switched Ethernet network?

Introduction / Context:
In a switched Ethernet network, loop free topology is essential to prevent frames from circulating endlessly. Spanning Tree Protocol (STP) is the standard mechanism that detects and logically disables redundant paths so that there is only one active path between any two points. When multiple physical links exist and STP is disabled, switching loops are created. This question is testing whether you understand that redundant links without STP cause broadcast storms rather than automatic load balancing or simple table issues.

Given Data / Assumptions:

• There are two switches connected by two crossover cables, creating two parallel layer 2 links.
• Spanning Tree Protocol is completely disabled on both switches.
• The switches are operating as normal transparent bridges that forward frames based on MAC addresses.
• End devices are sending unicast, multicast, and broadcast traffic over the network.

Concept / Approach:
When there are redundant layer 2 paths and no loop prevention mechanism, frames can circulate indefinitely. Broadcast frames and unknown unicast frames are flooded out all ports in the same VLAN except the one on which they are received. With two parallel links between switches, a flooded frame can travel back and forth, being copied repeatedly and never aged out. This creates a broadcast storm, consuming bandwidth and switch CPU resources and eventually leading to network collapse. STP prevents this by blocking one of the redundant links, but since STP is disabled in this scenario, the protection is not present.

Step-by-Step Solution:
1. Recognize that two crossover cables between the same pair of switches create a physical loop at layer 2. 2. Note that STP is disabled, so the switches will not logically block any of the redundant ports. 3. Understand that when a broadcast or unknown unicast frame is received, the switch floods it out all other ports in the same VLAN. 4. The flooded frame travels over both links to the other switch, which also floods it back, creating a loop. 5. New copies of the same frame continue to circulate, building into a broadcast storm that overwhelms the network. 6. Conclude that the correct effect is a broadcast storm on the switched network.

Verification / Alternative check:
In real networks, if you connect two switches with multiple links and disable STP, you will typically see immediate symptoms such as extremely high CPU utilization on the switches, massive increases in broadcast traffic, and loss of connectivity for normal data flows. Network monitoring tools will show an abnormal amount of broadcast frames. When STP is reenabled or one of the redundant links is removed, the storm stops, confirming that the loop and lack of STP were the causes.

Why Other Options Are Wrong:
Option a: Routing tables are a layer 3 concept and switches at layer 2 do not rely on them for basic forwarding, so this is not the main issue. Option b: The MAC table may change rapidly due to the loop, but the key problem is not a failure to update; it is the uncontrolled flooding. Option d: Standard switches do not automatically load balance at layer 2 over parallel links without additional features such as EtherChannel and proper configuration. Option e: Without STP or link aggregation protocols, both physical links are active and used for flooding, which contributes to the loop instead of leaving one link idle.

Common Pitfalls:
Learners sometimes think that more physical links always improve redundancy and performance automatically. However, at layer 2, redundant links require STP or another loop prevention system. Another pitfall is confusing broadcast storms with simple high utilization due to a heavy workload. Broadcast storms are self sustaining and continue even without new user traffic, which can make troubleshooting difficult. Remember that STP is the default safeguard, and disabling it in a network with redundant links almost always leads to broadcast storm scenarios.

Final Answer:
The most likely result is that broadcast storms will occur on the switched network when STP is disabled and redundant links are present.