Which option is the Cisco recommended over-subscription ratio for uplinks between the distribution and core layers?

An engineer is considering uplink bandwidth over-subscription in a Layer 3 network design.

Which option is the Cisco recommended over-subscription ratio for uplinks between the distribution and core layers?
A . 3 to 1
B . 4 to 1
C . 6 to 1
D . 8 to 1

View Answer

Answer: B

Explanation:

Network oversubscription refers to a point of bandwidth consolidation where the ingress bandwidth is greater than the egress bandwidth. For example, at an ISL uplink from an edge layer switch to a core, the oversubscription of the ISL is typically on the order of 7:1 or greater. In a single director fabric, the fan-out ratio of server to storage subsystem ports is directly related to the network oversubscription and is typically on the order of 10:1 or higher. Network oversubscription is normal and unavoidable-it is a direct by product of the primary purpose for deploying a SAN. An important characteristic of the network related to oversubscription is its ability to fairly allocate its bandwidth resources among all clients of the SAN.