Quick Answer
The answer is 1500 bytes. This is the correct maximum MTU for Cloud Router with Dedicated Interconnect because the on-premises MTU is already set to 1500, and the interconnect path adds a 4-byte 802.1Q VLAN tag and a 4-byte outer Ethernet header, which reduces the effective payload size for jumbo frames to 1440 bytes—but the Cloud Router interface MTU must match the on-premises endpoint to prevent fragmentation. On the Google Professional Cloud Network Engineer exam, this tests your understanding that Dedicated Interconnect handles encapsulation overhead transparently at the VLAN attachment level, so the Cloud Router MTU should mirror the customer’s on-premises MTU rather than being set higher. A common trap is assuming you can set the Cloud Router MTU to 1440 bytes to account for overhead, but that would cause fragmentation of 1500-byte packets from on-premises. Memory tip: “Match the MTU to the source—1500 is the course.”
This PCNE practice question tests your understanding of implementing hybrid interconnectivity. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company has deployed Dedicated Interconnect with a 10 Gbps connection. They are experiencing packet loss when transferring large files. The on-premises MTU is set to 1500. What is the maximum MTU that can be set on the Cloud Router interface to avoid fragmentation?
1460 bytes
Why wrong: 1460 is typical for PPPoE, not relevant here.
1500 bytes
Must match the on-premises MTU to avoid fragmentation.
1400 bytes
Why wrong: Too low; not necessary.
8896 bytes
Why wrong: While supported on Google Cloud side, the on-premises MTU of 1500 would cause fragmentation if packets exceed 1500.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
1500 bytes
Dedicated Interconnect uses VLAN attachments that encapsulate packets with an additional 4-byte 802.1Q VLAN tag and a 4-byte outer Ethernet header. With an on-premises MTU of 1500 bytes, the maximum payload that can traverse the interconnect without fragmentation is 1500 bytes, because the interconnect path supports jumbo frames up to 1440 bytes for the payload after overhead, but the Cloud Router interface MTU must match the on-premises MTU to avoid fragmentation. Setting the Cloud Router MTU to 1500 bytes ensures that packets are not fragmented at the router, as the interconnect handles the encapsulation overhead transparently.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
1460 bytes
Why it's wrong here
1460 is typical for PPPoE, not relevant here.
1500 bytes
Why this is correct
Must match the on-premises MTU to avoid fragmentation.
Related concept
Read the scenario before looking for a memorised answer.
1400 bytes
Why it's wrong here
Too low; not necessary.
8896 bytes
Why it's wrong here
While supported on Google Cloud side, the on-premises MTU of 1500 would cause fragmentation if packets exceed 1500.
Common exam traps
Google Cloud often tests the misconception that the Cloud Router MTU must be reduced to account for VLAN encapsulation overhead, but in Google Cloud Dedicated Interconnect, the Cloud Router MTU should match the on-premises MTU because the interconnect handles the additional headers transparently.
Detailed technical explanation
Dedicated Interconnect uses VLAN attachments with a 4-byte 802.1Q tag, but the Cloud Router interface MTU is set independently; the interconnect itself supports up to 1440 bytes of payload after overhead, but the Cloud Router MTU should match the on-premises MTU (1500) to avoid fragmentation at the router level. In practice, the interconnect path can handle jumbo frames up to 8896 bytes, but the bottleneck is the on-premises MTU; setting the Cloud Router MTU to 1500 ensures that packets are not fragmented before entering the interconnect, while the interconnect handles any necessary encapsulation. A common real-world scenario is when an on-premises device has a 1500 MTU and the Cloud Router is set to 1500, but the interconnect's VLAN tag causes the packet to exceed the path MTU; however, Google's infrastructure automatically handles this by using jumbo frames internally, so no fragmentation occurs.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
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FAQ
Implementing hybrid interconnectivity — This question tests Implementing hybrid interconnectivity — Read the scenario before looking for a memorised answer..
The correct answer is: 1500 bytes — Dedicated Interconnect uses VLAN attachments that encapsulate packets with an additional 4-byte 802.1Q VLAN tag and a 4-byte outer Ethernet header. With an on-premises MTU of 1500 bytes, the maximum payload that can traverse the interconnect without fragmentation is 1500 bytes, because the interconnect path supports jumbo frames up to 1440 bytes for the payload after overhead, but the Cloud Router interface MTU must match the on-premises MTU to avoid fragmentation. Setting the Cloud Router MTU to 1500 bytes ensures that packets are not fragmented at the router, as the interconnect handles the encapsulation overhead transparently.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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