In preparation for the deployment, what statement is correct from the below?

Question

Options

• AIt is best if you migrate Layer 2 functionality (e.g., VLAN tagging on uplinks) and Layer 3 function
• BIf you have spent good time on your design, there is no need to have any rollback plan
• CIt is not best practice to build the new network in parallel to the existing network
• DMigrate Layer 2 functionality (e.g., VLAN tagging on uplinks) then cut over to Layer 3 function

• A
  3% (1)
• B
  6% (2)
• C
  3% (1)
• D
  89% (32)

Explanation

D is correct because network migration must follow the OSI model's logical dependency: Layer 3 (routing/IP) cannot function without Layer 2 (switching/VLANs) being in place first. Migrating L2 (VLAN tagging, uplinks) first, then cutting over L3 (routing) ensures each layer is validated before the next depends on it - reducing risk and simplifying troubleshooting.

Why the distractors fail:

• A is wrong because it implies migrating L2 and L3 simultaneously, which is risky and makes it harder to isolate failures during cutover.
• B is dangerously wrong - a rollback plan is always required, regardless of design quality. Execution can fail even with a perfect design, and without a rollback you have no recovery path.
• C is the opposite of best practice. Building the new network in parallel to the existing one is best practice - it lets you test and validate before cutting over, minimizing downtime.

Memory tip: Think "OSI order = migration order." You build Layer 2 before Layer 3 in the OSI model, so you migrate L2 before L3 in deployment. If you remember that L3 rides on top of L2, the sequence becomes obvious.

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