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350-701 · Question #582

Client workstations are experiencing extremely poor response time. An engineer suspects that an attacker is eavesdropping and making independent connections while relaying messages between victims…

The correct answer is D. Dynamic ARP Inspection. The described attack, where an attacker relays messages to impersonate legitimate connections, is a Man-in-the-Middle (MITM) attack often enabled by ARP spoofing; Dynamic ARP Inspection (DAI) is designed to mitigate such attacks.

Submitted by dimitri_ru· Mar 30, 2026Network Security

Question

Client workstations are experiencing extremely poor response time. An engineer suspects that an attacker is eavesdropping and making independent connections while relaying messages between victims to make them think they are talking to each other over a private connection. Which feature must be enabled and configured to provide relief from this type of attack?

Options

  • ALink Aggregation
  • BReverse ARP
  • Cprivate VLANs
  • DDynamic ARP Inspection

How the community answered

(31 responses)
  • A
    6% (2)
  • B
    3% (1)
  • C
    13% (4)
  • D
    77% (24)

Why each option

The described attack, where an attacker relays messages to impersonate legitimate connections, is a Man-in-the-Middle (MITM) attack often enabled by ARP spoofing; Dynamic ARP Inspection (DAI) is designed to mitigate such attacks.

ALink Aggregation

Link Aggregation combines multiple physical network links into a single logical link for increased bandwidth and redundancy, not for preventing MITM attacks.

BReverse ARP

Reverse ARP (RARP) is used by a device to discover its IP address from its MAC address, which is not relevant to preventing MITM attacks.

Cprivate VLANs

Private VLANs (PVLANs) isolate ports within a VLAN at Layer 2, enhancing security by restricting communication between endpoints, but they do not specifically prevent ARP spoofing-based MITM attacks.

DDynamic ARP InspectionCorrect

Dynamic ARP Inspection (DAI) prevents Man-in-the-Middle (MITM) attacks by validating ARP packets in a network, ensuring that only valid ARP requests and responses are relayed, thereby preventing attackers from poisoning ARP caches and intercepting traffic.

Concept tested: Dynamic ARP Inspection (DAI) against MITM

Source: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/3se/security/configuration_guide/b_sec_3se_3850_cg/b_sec_3se_3850_cg_chapter_0100.html

Topics

#Dynamic ARP Inspection#ARP spoofing#Man-in-the-Middle#Layer 2 security

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