352-001 Question #752: Real Exam Question with Answer & Explanation

The correct answer is D: PMTUD. The correct answer is (D) PMTUD (Path MTU Discovery). Tunnel protocols like PPPoE, IPsec, and GRE all add encapsulation headers that reduce the effective Maximum Transmission Unit (MTU) available for the payload. Without PMTUD, the sending host is unaware of this reduced MTU, cau

Question

Your company utilizes many types of network transports, and you want to increase the efficiency of the network. Which solution can be used to improve network efficiency over PPPoE, IPsec and GRE networks?

Options

AOTAM
BIRDP
CHost Discovery Protocol
DPMTUD

Explanation

The correct answer is (D) PMTUD (Path MTU Discovery). Tunnel protocols like PPPoE, IPsec, and GRE all add encapsulation headers that reduce the effective Maximum Transmission Unit (MTU) available for the payload. Without PMTUD, the sending host is unaware of this reduced MTU, causing oversized packets to be fragmented or silently dropped mid-path, which wastes bandwidth and increases CPU overhead on intermediate devices. PMTUD (defined in RFC 1191 for IPv4 and RFC 8201 for IPv6) allows end hosts to dynamically discover the smallest MTU along the entire path and adjust their segment sizes accordingly, preventing fragmentation and improving overall network efficiency. OTAM (A) is not a standard networking protocol. IRDP (B) (ICMP Router Discovery Protocol) helps hosts discover default gateways and is unrelated to MTU efficiency. Host Discovery Protocol (C) is not a recognized standard for this purpose.

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