You are presented with requirements to design a development, testing and production environments. These environment should communicate with each other, yet they should be kept as separate failure…

OSPF is an IGP that operates within a single routing domain - all routers share the same LSDB, meaning a topology failure propagates to all routers rather than being contained to a separate domain.

EIGRP, while using AS numbers, is still an IGP designed for intra-domain routing and does not provide the policy controls or domain isolation that BGP offers between separate administrative boundaries.

IS-IS is a link-state IGP similar to OSPF and operates within a single IS-IS domain, providing no mechanism to isolate failure domains between separate network environments.

BGP is the only protocol among the choices that natively separates administrative and failure domains via Autonomous System (AS) numbers. Each environment (dev, test, prod) can reside in its own AS, isolating routing failures to that domain while still allowing controlled inter-AS route advertisement using BGP policies such as route maps and prefix filters.