Which function is performed at the access layer of the three-layer hierarchical network design model?
Correct Answer:
B
In the Cisco three-layer hierarchical design model (Access, Distribution, Core), the access layer is primarily responsible for:
Providing user/device connectivity.
Enforcing policy boundaries.
Performing QoS classification and marking at ingress.
The access layer is the optimal point to classify and mark traffic for QoS because:
It is the first point of entry into the network for end-user devices.
Markings can then be trusted by upstream devices (distribution and core).
This minimizes trust boundaries throughout the network and ensures consistent policy enforcement.
This design principle ensures end-to-end QoS consistency, a key objective emphasized in CCDE v3.1 for scalable and maintainable enterprise designs.
Why other options are incorrect:
A (Fault isolation): Typically handled at distribution/core layers.
C (Reliability): A general network-wide requirement, not specific to access.
D (Fast transport): Primarily a core layer function.
E (Redundancy and load balancing): Managed primarily at distribution and core layers.
