1Z0-1124-25 practice question 15 of 25

You are designing a highly available web application in OCI. You’ve created a VCN with two public subnets across different Availability Domains…

You are designing a highly available web application in OCI. You’ve created a VCN with two public subnets across different Availability Domains (ADs). You need to enable IPv6 support for the application to cater to a growing number of IPv6-only clients. You plan to use a Load Balancer to distribute traffic to backend compute instances in the public subnets. Which of the following approaches ensures the highest level of resilience and IPv6 connectivity for your application?

Answer options

A: Configure the VCN with a /48 IPv6 ULA prefix. Configure the Load Balancer to listen on IPv4 only, and the compute instances to listen on both IPv4 and IPv6, relying on NAT for IPv6 clients.

B: Configure the VCN with a /48 IPv6 ULA prefix. Configure the Load Balancer to listen on both IPv4 and IPv6 addresses. Ensure the backend compute instances also listen on both IPv4 and IPv6 addresses. Route traffic accordingly using NSGs.

C: Configure the VCN with a public IPv6 CIDR block obtained from Oracle. Configure the Load Balancer to listen on IPv4 only, while backend compute instances listen on both IPv4 and IPv6, relying on NAT for IPv6 clients.

D: Configure the VCN with a public IPv6 CIDR block obtained from Oracle. Configure the Load Balancer to listen on both IPv4 and IPv6 addresses. Ensure the backend compute instances also listen on both IPv4 and IPv6 addresses. Correct answer

Correct Answer:

D. Configure the VCN with a public IPv6 CIDR block obtained from Oracle. Configure the Load Balancer to listen on both IPv4 and IPv6 addresses. Ensure the backend compute instances also listen on both IPv4 and IPv6 addresses.

Explanation

Requirements: HA and IPv6 support for public web app.
Option A: ULA is private, not routable; NAT for IPv6 is inefficient—incorrect.
Option B: ULA doesn’t support public IPv6 clients—incorrect.
Option C: Public IPv6 CIDR is correct, but IPv4-only LB with NAT lacks direct IPv6—less resilient.
Option D: Public IPv6 CIDR with dual-stack LB and instances ensures full IPv6 support and HA across ADs—correct. Conclusion: Option D maximizes resilience and connectivity. Oracle states: "For public IPv6 applications, use a public IPv6 CIDR block and configure Load Balancers and instances for both IPv4 and IPv6 to ensure resilience." This supports Option D. Reference: IPv6 in OCI - Oracle Help Center (docs.oracle.com/en- us/iaas/Content/Network/Tasks/managingIPv6.htm).

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