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Difficulty: HardComparing Traditional Networks with Controller-Based Networking

An enterprise networking team is replacing a legacy campus deployment of fifty access switches that suffer from configuration drift and inconsistent QoS policies. The team evaluates migrating to a software-defined network (SDN) architecture managed by a centralized controller such as Cisco DNA Center. Which statement correctly contrasts how control plane state and policy management differ between these two architectures?

  1. The controller centralizes policy logic and abstracts device provisioning through Southbound APIs such as NETCONF to communicate with network hardware, whereas traditional switches build routing and forwarding decisions independently using distributed control plane protocols.Answer
  2. B
    The controller relies on RESTful HTTP GET requests to push and overwrite device configuration states across access switches, whereas traditional switches require out-of-band SNMP traps for configuration deployment.
  3. C
    The controller requires a dedicated software agent installed on each switch's operating system to interpret configuration pushes, whereas traditional switch management requires an agentless infrastructure driven by local Python scripts.
  4. D
    The controller operates as a Type 2 hosted hypervisor directly on switch physical ASICs to handle packet switching, whereas traditional switches rely on Type 1 bare-metal hypervisors to manage physical interface states.

Answer

The controller centralizes policy logic and abstracts device provisioning through Southbound APIs such as NETCONF to communicate with network hardware, whereas traditional switches build routing and forwarding decisions independently using distributed control plane protocols.
In controller-based SDN environments, control plane intelligence is centralized on the controller, which programs network forwarding hardware using Southbound APIs (such as NETCONF or RESTCONF). Traditional networks employ a distributed control plane where each network device independently processes control protocols and requires individual device configuration.

Step-by-Step Solution

1
Analyze control plane operation in traditional networking
In traditional networking, the control plane is distributed across every device. Each switch and router runs its own control plane protocols (like OSPF, EIGRP, STP) locally to make independent forwarding decisions.
Understanding distributed control planes provides the baseline for structural comparison.
2
Analyze control plane operation in controller-based (SDN) networking
In controller-based architectures (SDN), control plane intelligence is decoupled from forwarding devices and centralized within an SDN controller (e.g., Cisco DNA Center).
Centralization enables network-wide policy management and automated provisioning.
3
Identify the communication interfaces (Southbound vs Northbound APIs)
The SDN controller communicates down to infrastructure devices using Southbound APIs (NETCONF, RESTCONF, OpenFlow) and exposes Northbound APIs (RESTful HTTP) to management applications and orchestration tools.
API distinction is a key operational difference between traditional CLI/SNMP management and controller-driven management.

Key Concept

Comparing Traditional Networks with Controller-Based Networking
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Topics

Comparing Traditional Networks with Controller-Based Networking

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