CAS-002 · Question #37
Company GHI consolidated their network distribution so twelve network VLANs would be available over dual fiber links to a modular L2 switch in each of the company's six IDFs. The IDF modular…
The correct answer is B. Threat: Bridge loop. The scenario describes dual fiber links (redundant physical paths) connected to Layer 2 switches across multiple IDFs. On a Layer 2 network without loop prevention, redundant links create the conditions for a bridge loop (switching loop). Unlike higher-layer protocols, Ethernet…
Question
Company GHI consolidated their network distribution so twelve network VLANs would be available over dual fiber links to a modular L2 switch in each of the company's six IDFs. The IDF modular switches have redundant switch fabrics and power supplies. Which of the following threats will have the GREATEST impact on the network and what is the appropriate remediation step?
Options
- AThreat: 802.1q trunking attack
- BThreat: Bridge loop
- CThreat: VLAN hopping
- DThreat: VLAN hopping
How the community answered
(48 responses)- A23% (11)
- B60% (29)
- C6% (3)
- D10% (5)
Explanation
The scenario describes dual fiber links (redundant physical paths) connected to Layer 2 switches across multiple IDFs. On a Layer 2 network without loop prevention, redundant links create the conditions for a bridge loop (switching loop). Unlike higher-layer protocols, Ethernet has no TTL mechanism, so broadcast frames loop indefinitely, causing a broadcast storm that consumes all available bandwidth and brings down the entire network - the greatest possible impact. The remediation is to enable Spanning Tree Protocol (STP) or its faster variant RSTP, which logically blocks redundant paths while keeping them available for failover. VLAN hopping and 802.1q attacks are serious but do not carry the same potential for total network collapse.
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