Which function is performed by the collapsed core layer in a two-tier architecture?

The collapsed core layer consolidates the functions of the traditional core and distribution layers, including high-speed routing, inter-VLAN routing, and the enforcement of routing policies to manage traffic flow between different network segments.

While the distribution layer (part of the collapsed core) can mark traffic, the primary and most defining function of the collapsed core is routing policy enforcement and high-speed forwarding.

Attaching users to the network edge is the fundamental function of the access layer in a hierarchical design.

Applying security policies is a function that can occur at the distribution or core layer, but enforcing routing policies is a more direct and fundamental role of the collapsed core's routing capabilities.