Traditional networks vs controller-based networking
5 minutes
5 Questions
Traditional networks rely on a distributed architecture where each network device (routers, switches, firewalls) operates independently with its own control plane and data plane. Network administrators must configure each device individually using command-line interfaces (CLI), which becomes time-c…Traditional networks rely on a distributed architecture where each network device (routers, switches, firewalls) operates independently with its own control plane and data plane. Network administrators must configure each device individually using command-line interfaces (CLI), which becomes time-consuming and error-prone as networks grow. Changes require manual intervention on multiple devices, making scalability challenging and increasing the risk of configuration inconsistencies.
Controller-based networking, also known as Software-Defined Networking (SDN), separates the control plane from the data plane. A centralized controller manages network intelligence and decision-making, while network devices focus solely on forwarding traffic based on instructions received from the controller. This architecture introduces three distinct planes: the management plane (user interface), control plane (centralized controller), and data plane (network devices).
Key differences include:
1. **Management Approach**: Traditional networks require device-by-device configuration, while controller-based networks enable centralized management through a single point of control.
2. **Programmability**: SDN controllers expose APIs (Application Programming Interfaces) that allow automation tools and custom applications to interact with the network programmatically. Traditional networks have limited automation capabilities.
3. **Scalability**: Controller-based networks can push configuration changes to hundreds of devices simultaneously, while traditional networks require individual device updates.
4. **Visibility**: SDN provides a holistic network view from the controller, whereas traditional networks offer fragmented visibility per device.
5. **Flexibility**: Policy changes in SDN can be implemented network-wide through the controller, making adaptation to business requirements more efficient.
Cisco DNA Center and Cisco ACI are examples of controller-based solutions. These platforms use intent-based networking principles, where administrators define desired outcomes, and the controller translates these into device configurations.
For CCNA candidates, understanding this evolution is essential as modern enterprise networks increasingly adopt controller-based architectures to support automation, improve operational efficiency, and enable rapid deployment of network services.
Traditional Networks vs Controller-Based Networking
Why This Topic Is Important
Understanding the differences between traditional and controller-based networking is fundamental to the CCNA exam. Cisco emphasizes network automation and programmability as the industry shifts toward software-defined solutions. This topic typically accounts for 10% of the exam and tests your ability to recognize architectural differences, benefits, and use cases.
What Are Traditional Networks?
Traditional networks use a distributed architecture where each network device (router, switch, firewall) operates independently. Key characteristics include:
• Distributed Control Plane: Each device makes its own forwarding decisions based on locally stored routing tables and protocols • Device-by-Device Configuration: Administrators must configure each device individually via CLI • Manual Management: Changes require logging into each device separately • Protocol-Based Communication: Devices share information through routing protocols like OSPF, EIGRP, and BGP • Hardware-Centric: Features are tied to the physical device capabilities
What Is Controller-Based Networking?
Controller-based networking uses a centralized architecture where a software controller manages network devices. Key characteristics include:
• Centralized Control Plane: A controller makes decisions for the entire network • Separation of Planes: The control plane is separated from the data plane • Programmatic Interface: Networks can be configured through APIs (REST, NETCONF, RESTCONF) • Single Point of Management: One interface to manage all devices • Software-Defined: Network behavior is determined by software rather than individual device configurations
How It Works: The Three Planes
Management Plane: • Handles device access (SSH, SNMP, APIs) • Used for monitoring and configuration • In controller-based networks, this connects to the controller
Control Plane: • Makes forwarding decisions • Runs routing protocols and builds tables • Traditional: Distributed across devices • Controller-based: Centralized in the controller
Data Plane: • Forwards traffic based on control plane decisions • Remains on individual devices in both architectures • Also called the forwarding plane
Key Differences Comparison
Configuration: • Traditional: CLI on each device • Controller-based: Centralized GUI or API
Scalability: • Traditional: More complex as network grows • Controller-based: Scales more efficiently
Consistency: • Traditional: Risk of configuration drift • Controller-based: Uniform policies across network
Troubleshooting: • Traditional: Check each device individually • Controller-based: Centralized visibility and analytics
Flexibility: • Traditional: Limited by device capabilities • Controller-based: Programmable and adaptable
Cisco Controller Solutions
• Cisco DNA Center: Enterprise network controller for campus and branch • Cisco ACI: Application Centric Infrastructure for data centers • Cisco SD-WAN (vManage): Controller for WAN environments • Cisco Meraki Dashboard: Cloud-managed networking
Southbound and Northbound Interfaces
Southbound Interfaces (SBI): Communication between controller and network devices • OpenFlow • NETCONF • RESTCONF • CLI (legacy)
Northbound Interfaces (NBI): Communication between controller and applications • REST APIs • Used by business applications and automation tools
Exam Tips: Answering Questions on Traditional vs Controller-Based Networking
1. Know the Terminology: Understand terms like SDN (Software-Defined Networking), control plane, data plane, and management plane
2. Focus on Centralization: When a question mentions centralized management or a single point of control, think controller-based
3. Remember API Types: REST APIs are for northbound interfaces; NETCONF and RESTCONF are southbound protocols
4. Identify Keywords: Words like automation, programmability, and orchestration point toward controller-based solutions
5. Understand Trade-offs: Controller-based adds a potential single point of failure but provides better scalability and consistency
6. Know Cisco Products: Be familiar with DNA Center for enterprise and ACI for data center contexts
7. Control Plane Location: If asked where the control plane resides, remember it is distributed in traditional networks and centralized in controller-based
8. Scenario Questions: For large-scale deployments requiring consistent policies, controller-based is typically the correct answer
9. Data Plane Stays Local: Regardless of architecture, the data plane always remains on the individual network devices
10. Elimination Strategy: If an answer mentions configuring each device separately for large networks, it likely describes traditional networking limitations