Introduction

The exam topics on the CCNA Routing & Switching exam (current version 200-125) are broken down into seven sections, one of which is network fundamentals. In this article, we will discuss this section and the topics it includes. We will present a high-level overview of the various topics and conclude with ideas on how best to study for this section of the exam.

What Percentage of the Exam Covers Networking Fundamentals?

While the percentages of the CCNA 200-125 exam are subject to change at any time, the networking fundamentals section currently covers 15% of the exam. Since the exam is currently 60-70 questions, you should expect nine or 10 questions on networking fundamentals.

What Topics are Covered in This Section of the Exam?

There are various topics under the networking fundamentals section of the exam. These topics are actually divided into 15 sub-sections, from 1.1 to 1.15. However, these topics each fall under one of the following broad categories:

  • OSI and TCP/IP Models, including TCP/UDP protocols
  • Infrastructure components such as firewalls, routers and access points, including cloud resources
  • Network topologies and architectures, including cabling
  • IPv4 addressing, including identification, configuration and troubleshooting
  • IPv6 addressing, including identification, configuration and troubleshooting

High-Level Overview of Networking Fundamentals Topics

We will now look at the broad categories listed above in a bit more detail and discuss the knowledge required of you for each topic.

OSI and TCP/IP Models

The exam topic actually reads compare and contrast OSI and TCP/IP models. However, comparing two things means you need to have an understanding of each. Both the OSI and TCP/IP models are reference models used to describe network communications. They are different because they were created by two separate entities, but they also have similarities.

The OSI model is probably one of the first things you are going to learn as a newcomer to networking. For the exam, you should be familiar with the seven layers of the OSI model, as well as the various protocols and devices that operate at the different layers. For example, TCP and UDP operate at the transport layer of the OSI model, and another topic on the exam is compare and contrast TCP and UDP protocols.

On the other hand, the TCP/IP model is a four-layer model that is more in line with modern-day networking communication. For the exam, you should be familiar with the four layers of the TCP/IP model, as well as the protocols and devices that operate at the different layers. You should also know how the layers of the TCP/IP model map to the layers of the OSI model.

You can read some articles on the InfoSec Institute site that describe these topics here and here.

Infrastructure Components and Cloud Resources

When you think about it, a network is just a set of connected devices. However, different devices on the network have different functions: Some facilitate communication while some rely on the network to communicate. For this category of the exam, you should be familiar with devices that facilitate communication — that is, the underlying network infrastructure including wireless access points, routers, switches, firewalls and so on.

As more networks are relying on the cloud, you should also understand and be able to describe the effects of cloud resources on enterprise network architecture. You need to be able to differentiate the different types of clouds (private, public and hybrid, among others) and understand how the enterprise network will be connected to this cloud infrastructure (VPN, leased line and so forth). You should also be able to describe various virtual services such as DNS and DHCP, and basic virtual network infrastructure such as virtual firewalls and virtual routers.

Network Topologies and Architectures

When designing a network, there are some sound engineering principles that should be adhered to, including hierarchy, modularity, resiliency and flexibility. You should be familiar with Cisco’s network design models that incorporate these principles. The most famous of these design models is the hierarchical design model, in which a network is traditionally divided into the access, distribution, and core layers — a three-tier architecture. Even though Cisco has since moved past this hierarchical design model to newer models, it still finds application in some parts of the network, such as the enterprise campus network.

For the exam, you need to be familiar with these three layers of a network and able to identify the devices and services at the different layers. For example, the access layer is where you have IP phones and end-user devices.

Depending on the size of a network, the core layer and distribution layer may be collapsed into a single unit known as a collapsed core. According to the exam topic, you need to be able to compare and contrast collapsed core and three-tier architectures.

Going into the exam, you also need to understand the various network topologies, including star, mesh, hybrid and so on. For example, in a wide area network (WAN), you can either use a star topology, in which branch sites are connected to one or two hub sites, or you could go for a mesh topology, in which all sites are connected to each other. You can also have a mix of both. Of course, you should be familiar with the benefits and disadvantages of each topology.

Finally, you should be able to select the appropriate cabling type based on implementation requirements. For example, you should know the difference between copper cables (like STP) and optical cables (like fiber). You will need to understand the various Ethernet standards for these different cables and the limitations of these technologies, such as the 100-meter distance limitation of copper cables.

Tip: You should be able to answer a question like: which SFP module will you use for distance up to 80km? SX, LR or ZR? (The correct answer is ZR.)

IPv4 Addressing

Almost all forms of networks today rely on IP addressing, of which there are two main versions: IP version 4 (IPv4) and IP version 6 (IPv6). For the exam, you should understand what an IP address is and how it facilitates communication on a network. You should be able to compare and contrast the different types of IPv4 addresses — unicast, broadcast and multicast.

This topic is one of those where the exam uses words like configure, verify and troubleshoot. This means that you should expect to get lab and simulation questions on this topic. Not only should you be able to configure an IP address on, say, a router interface, but you must also be able to figure out if communication is not happening between two devices because of, for example, a wrongly-configured subnet mask.

The CCNA exam is also big on subnetting, so you should be able to answer questions like the number of hosts that can fit a particular subnet (prefix length), the number of subnets that can be created from a particular address block, the address range of a given subnet, the broadcast address of a given subnet, if two addresses belong on the same subnet, and so on.

Finally, you should be aware of the exhaustion of IPv4 addresses and the techniques for overcoming this issue, including private IPv4 addressing (RFC 1918), classless inter-domain routing (CIDR), network address translation (NAT) and IPv6.

You can view this CCNA Cheat Sheet from InfoSec Institute for a brief guide on IPv4 addressing.

IPv6 Addressing

While IPv6 addressing was glossed over in previous versions of the CCNA exam, there is now a huge focus on it in the current version of the exam as the world moves to embrace IPv6 addressing.

For the exam, not only should you know about IPv6 addressing, you must also be able to configure, verify, and troubleshoot IPv6 addressing. You must also be able to configure and verify IPv6 Stateless Address Auto Configuration.

For someone who is already comfortable with IPv4 addressing, IPv6 addressing can be a bit of a culture shock. The addresses are four times longer; the format of writing them is different; there are different types of IPv6 addresses, including link local, anycast and so on. All of this can be a bit overwhelming. Thankfully, there are many articles that have described IPv6 in detail. For example, there is a 13-part IPv6 series on the InfoSec Institute site, the first of which can be found here. You can search for the remaining articles in the series using this link.

Where Should I Focus My Time Studying?

Now that we have looked at the various topics in some detail, you may be wondering where to focus your study time. The network fundamentals section of the CCNA exam is the very first section for a reason: It lays a foundation for your understanding of networking. If you rush through this, you will have to make up for it later in your testing and your career as a whole. Therefore, I advise that you spend the maximum allowable time understanding the topics in this section.

From the perspective of passing the examination, you should thoroughly understand the OSI and TCP/IP models, including the devices and services/protocols that operate at each layer. Subnetting is another part that throws people off in the exam, so be sure to practice this a lot. Not only is subnetting important for the network fundamentals section, it will turn up all across the exam, such as in the sections on access control lists and routing. Also, since IPv6 may be new to many people, you should focus on understanding the different IPv6 address types and be able to identify them from their subnet prefixes.

Conclusion

In this article, we have looked at the first section in the CCNA 200-125 exam topics: network fundamentals. We have seen how this section lays the foundation for other sections of the exam by focusing on the basic knowledge of networking. We divided the topics in this exam section into five categories and looked at each category briefly. Finally, we highlighted some topics in this section that an exam candidate may want to focus on for the exam.

 

Sources

CCNA Exam Topics, The Cisco Learning Network

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