A network engineer is inspecting traffic behavior on a multilayer switch operating within a controller-managed fabric network. An ingress data packet matching an existing destination entry in the Forwarding Information Base (FIB) arrives at a switch port. At the same moment, an OSPF Hello packet arrives on the same physical port. Which statement correctly describes how the switch architecture handles these two incoming frames?
- The ingress data packet is forwarded directly by the data plane using specialized ASIC hardware, while the OSPF Hello packet is punted to the control plane CPU for processing.Answer
- BThe OSPF Hello packet is processed directly within the data plane ASIC to update the FIB in real time, while the ingress data packet is buffered in the control plane until neighbor adjacency is re-verified.
- CBoth the ingress data packet and the OSPF Hello packet are sent to the SDN controller via a Southbound API for flow table validation before hardware switching can occur.
- DThe ingress data packet is redirected to the management plane for Quality of Service (QoS) classification, while the OSPF Hello packet is forwarded by the data plane using MAC table lookup.
Answer
The ingress data packet is forwarded directly by the data plane using specialized ASIC hardware, while the OSPF Hello packet is punted to the control plane CPU for processing.
In modern networking devices and SDN architectures, the data plane (forwarding plane) utilizes specialized hardware (ASICs and TCAM) to forward transit user traffic at line rate based on pre-calculated table entries (FIB and Adjacency tables). Conversely, control plane protocols (such as OSPF, BGP, and ARP) require protocol state processing and decision logic, which is handled by the control plane CPU. Therefore, the data packet is switched in hardware by the data plane, while the OSPF Hello frame is punted to the control plane CPU.
Step-by-Step Solution
Key Concept
Separation of Control Plane and Data Plane Responsibilities