Explanation https://www.omnisecu.com/cisco-certified-network-associate-ccna/three-tier-hierarchical-network-model.php Core Layer consists of biggest, fastest, and most expensive routers with the highest model numbers and Core Layer is considered as the back bone of networks. Core Layer routers are used to merge geographically separated networks. The Core Layer routers move information on the network as fast as possible. The switches operating at core layer switches packets as fast as possible.