For a fully redundant connection from an on-premises data center to a VCN in the OCI us-ashburn-1 region, it is important to ensure high availability and fault tolerance. Here's how each option contributes to redundancy:

Option B: Two FastConnect Virtual Circuits:

FastConnect provides a dedicated, private connection with higher bandwidth and more consistent performance compared to a VPN. To achieve redundancy, you can configure two FastConnect circuits in the same region (us-ashburn-1), each terminated on diverse hardware on-premises. This setup ensures that even if one circuit or its associated hardware fails, the other circuit can maintain the connection. This ensures no single point of failure in the connectivity to OCI. Thus, option B is correct.

Option D: FastConnect and Site-to-Site VPN:

Another approach to redundancy is to have a mix of connection types. By setting up one FastConnect circuit and one Site-to-Site VPN, both terminating in the same region (us-ashburn-1), you create a diverse connection path. If the FastConnect connection fails, traffic can automatically route through the VPN connection, maintaining connectivity. This setup adds an extra layer of redundancy, making option D correct as well.

Incorrect Options:

Option A: Only configuring a Site-to-Site VPN from a single on-premises CPE does not provide redundancy because it involves just one connection path. If that connection or the CPE fails, there would be no fallback.

Option C: Configuring FastConnect circuits to different regions (us-ashburn-1 and us-phoenix-1) does not provide redundancy within a single region but rather across regions, which is not required for regional redundancy.

Relevant OCI Documentation:

OCI FastConnect Overview

Using Site-to-Site VPN and FastConnect for Redundancy

These references offer more detailed information on setting up redundant connections and the benefits of each connection type within OCI.

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