The correct solution is a Data Center Interconnect (DCI). DCIs extend Layer 2 networks across geographically dispersed data centers, enabling seamless replication of services such as SAN storage, backup synchronization, or VM migrations. This ensures workloads and data can move between sites while maintaining the same VLANs and addressing.

A . Security Service Edge (SSE) provides cloud-delivered security functions like secure web gateways and CASB, not Layer 2 extension.

C . Infrastructure as code (IaC) automates deployment and management of network infrastructure but is unrelated to extending Layer 2 domains.

D . Zero Trust architecture is a security framework ensuring strict access control but doesn't address network connectivity between sites.

In scenarios where backups need replication between sites, Layer 2 extension is often required so systems can communicate as if they are in the same broadcast domain. DCI is specifically designed to provide this functionality reliably and securely.

Reference (CompTIA Network+ N10-009):

Domain: Network Infrastructure --- WAN technologies, data center interconnect, backup replication.