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PCNE Practice Question: Managing, Monitoring, and Optimising Network Operations

A network engineer is troubleshooting connectivity issues between two Compute Engine instances in the same VPC but different subnets (us-east1 and europe-west1). The engineer suspects an MTU issue. What is the default MTU for traffic within Google Cloud, and what MTU should the engineer expect when packets traverse the internet?

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

1460 bytes internally, 1500 bytes internet

Google Cloud uses an MTU of 1460 bytes (64 bytes less than the standard 1500) to accommodate encapsulation headers. Internet traffic typically uses 1500 bytes. Fragmentation can occur if a packet larger than 1460 bytes is sent over a path that expects 1500 but the internal path is 1460.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • 1400 bytes internally, 1500 bytes internet

    Why it's wrong here

    Incorrect: internal MTU is 1460, not 1400.

  • 1460 bytes internally, 1500 bytes internet

    Why this is correct

    Correct: GCP internal MTU is 1460, internet standard is 1500.

  • 1500 bytes both internally and internet

    Why it's wrong here

    Incorrect: internal MTU is 1460.

  • 1500 bytes internally, 1460 bytes internet

    Why it's wrong here

    Incorrect: internal MTU is 1460, not 1500.

Visual reference

192.168.1.0 /24 256 addresses (254 usable) 192.168.1.0 /25 Subnet A 128 addr (126 usable) 192.168.1.128 /25 Subnet B 128 addr (126 usable) Borrowing 1 bit from host portion creates 2 subnets (/25)

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JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

This PCNE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCNE exam.