This chapter covers the following exam topics:
1.0 Network Fundamentals
1.1 Explain the role and function of network components
1.2 Describe characteristics of network topology architectures
6.0 Automation and Programmability
6.1 Explain how automation impacts network management
6.2 Compare traditional networks with controller-based networking
6.3 Describe controller-based and software defined architectures (overlay, underlay, and fabric)
6.3.a Separation of control plane and data plane
6.3.b Northbound and southbound APIs
The CCNA certification focuses on the traditional model for operating and controlling networks, a model that has existed for decades. You understand protocols that the devices use, along with the commands that can customize how those protocols operate. Then you plan and implement distributed configuration to the devices, device by device, to implement the network.
The 2010s have seen the introduction of a new network operational model: Software Defined Networking (SDN). SDN makes use of a controller that centralizes some network functions. The controller also creates many new capabilities to operate networks differently; in particular, controllers enable programs to automatically configure and operate networks through power application programming interfaces (APIs).
With traditional networking, the network engineer configured the various devices and changes requiring a long timeframe to plan and implement changes. With controller-based networking and SDN, network engineers and operators can implement changes more quickly, with better consistency, and often with better operational practices.
This chapter introduces the concepts of network programmability and SDN. Note that the topic area is large, with this chapter providing enough detail for you to understand the basics and to be ready for the other three chapters in this part.
The first major section of this chapter introduces the basic concepts of data and control planes, along with controllers and the related architecture. The second section then shows separate product examples of network programmability using controllers, all of which use different methods to implement networking features. The last section takes a little more exam-specific approach to these topics, comparing the benefits of traditional networking with the benefits of controller-based networking.
“Do I Know This Already?” Quiz
Take the quiz (either here or use the PTP software) if you want to use the score to help you decide how much time to spend on this chapter. The letter answers are listed at the bottom of the page following the quiz. Appendix C, found both at the end of the book as well as on the companion website, includes both the answers and explanations. You can also find both answers and explanations in the PTP testing software.
Table 16-1 “Do I Know This Already?” Foundation Topics Section-to-Question Mapping
Foundation Topics Section
SDN and Controller-Based Networks
Examples of Network Programmability and SDN
Comparing Traditional and Controller-Based Networks
1. A Layer 2 switch examines a frame’s destination MAC address and chooses to forward that frame out port G0/1 only. That action occurs as part of which plane of the switch?
2. A router uses OSPF to learn routes and adds those to the IPv4 routing table. That action occurs as part of which plane of the switch?
3. A network uses an SDN architecture with switches and a centralized controller. Which of the following terms describes a function or functions expected to be found on the switches but not on the controller?
A northbound interface
A southbound interface
Data plane functions
Control plane functions
4. Which of the following controllers (if any) uses a mostly centralized control plane model?
Cisco Application Policy Infrastructure Controller (APIC)
Cisco APIC Enterprise Module (APIC-EM)
None of these controllers uses a mostly centralized control plane.
5. To which types of nodes should an ACI leaf switch connect in a typical single-site design? (Choose two answers.)
All of the other leaf switches
A subset of the spine switches
All of the spine switches
Some of the endpoints
None of the endpoints
6. Which answers list an advantage of controller-based networks versus traditional networks? (Choose two answers.)
The ability to configure the features for the network rather than per device
The ability to have forwarding tables at each device
Programmatic APIs available per device
More consistent device configuration
Answers to the “Do I Know This Already?” quiz:
5 C, D
6 A, D