350-501 Architecture Practice Question
A service provider is deploying a new metro Ethernet network and needs to support multiple customer VLANs over a single physical link without overlapping VLAN IDs. Which technology should be used at the access layer to achieve this?
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
✓
Q-in-Q (802.1ad) double tagging
Q-in-Q (802.1ad) allows service providers to add an outer VLAN tag to customer frames, enabling customer VLAN separation even when their VLAN IDs conflict. This is commonly used in metro Ethernet networks for scalability.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
VLAN translation
Why it's wrong here
VLAN translation modifies tags but does not inherently provide the scalability of double tagging for many customers.
- ✓
Q-in-Q (802.1ad) double tagging
Why this is correct
Correct. Q-in-Q adds an outer tag to segregate customer traffic, allowing overlapping inner VLANs.
- ✗
MAC-in-MAC (802.1ah)
Why it's wrong here
MAC-in-MAC is used for provider backbone bridging, not typically at the access layer for VLAN scalability.
- ✗
VLAN trunking with 802.1Q
Why it's wrong here
802.1Q only supports a single tag and cannot resolve overlapping VLAN IDs across customers.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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