300-420 Question 55
Single answerAn enterprise network is planning to migrate to dual-stacking IPv4 and IPv6 to support modern applications and ensure long-term scalability. The network engineer has deployed dual-stacking on the core and access layers. However, users report connectivity issues when accessing certain external servers. What is the MOST likely reason for this issue?
- A
The external servers do not support IPv6, and the enterprise has not implemented NAT64.
- B
The dual-stacked devices are using IPv6 exclusively, and IPv4 traffic is being dropped.
- C
The enterprise has not enabled OSPFv3 for IPv6 routing within its network.
- D
The dual-stacked devices are not configured with appropriate IPv6 addresses.
Show answer and explanation
Correct answer: A
Explanation
In a dual-stacked environment, both IPv4 and IPv6 are enabled, allowing devices to communicate over either protocol. However, if external servers only support IPv4, devices using IPv6 need a mechanism like NAT64 to translate IPv6 packets into IPv4 packets. Without this mechanism, connectivity to IPv4-only servers will fail, even though the enterprise network is dual-stacked.
- A. Correct.
Correct: If the external servers do not support IPv6 and the enterprise network is dual-stacked, NAT64 or another translation mechanism is necessary to allow IPv6-only clients to communicate with IPv4-only servers.
- B. Incorrect.
Incorrect: Dual-stacked devices use both IPv4 and IPv6. By design, they do not exclusively rely on IPv6 unless explicitly configured to do so, which is unlikely in this scenario.
- C. Incorrect.
Incorrect: While OSPFv3 is necessary for IPv6 routing, the scenario describes connectivity issues with external servers, not internal routing. OSPFv3 is unrelated to the problem described.
- D. Incorrect.
Incorrect: Missing or incorrect IPv6 address configurations would cause more widespread connectivity issues, not limited to specific external servers as described.