Helen has deployed both Cisco and Juniper routers in her organization to ensure that a vulnerability in one vendor's products does not result in a complete outage of her organization. What is this type of design called?

This type of architecture leverages the idea of platform diversity. Having multiple vendors and platforms helps to ensure that a single vendor's failure or vulnerability does not prevent an organization from continuing to function. Platform agnostic is not on the Security+ exam but typically means that organizations don't have a vested interest in which platform is selected or used. Multi-cloud environments run in multiple cloud vendors' tools, but this question involves physical router hardware. Parallel processing is a failure testing mode where two or more sites run at the same time during a test.