Only the EIGRP route will be placed in the routing table because EIGRP has the lowest administrative distance (AD), and that is always used before metrics. See Chapter 9 for more information.
22. D. Switches send information about only one VLAN down a link unless it is configured as a trunk link. See Chapter 11 for more information.
23. A. By default, switches break up collision domains on a per-port basis but are one large broadcast domain. See Chapter 1 for more information.
24. C, D. VLAN Trunking Protocol (VTP) is not right because it has nothing to do with trunking except that it sends VLAN information across a trunk link. 802.1q and ISL encapsulations are used to configure trunking on a port. See Chapter 11 for more information.
25. D. Stub networks have only one connection to an internetwork. Default routes should be set on a stub network or network loops may occur; however, there are exceptions to this rule. See Chapter 9 for more information.
26. B. Hubs regenerate electrical signals, which are specified at the Physical layer. See Chapter 1 for more information.
27. A, C. Standard and extended access control lists (ACLs) are used to configure security on a router. See Chapter 12 for more information.
28. C. If you start at 192.168.128.0 and go through 192.168.159.0, you can see that this is a block of 32 in the third octet. Since the network address is always the first one in the range, the summary address is 192.168.128.0. What mask provides a block of 32 in the third octet? The answer is 255.255.224.0, or /19. See Chapter 5 for more information.
29. B. The command to back up the configuration on a router is copy running-config startup-config. See Chapter 7 for more information.
30. C. IEEE 802.3ab is the standard for 1 Gbps on twisted-pair. See Chapter 2 for more information.
Chapter 1
Internetworking
THE FOLLOWING ICND1 EXAM TOPICS ARE COVERED IN THIS CHAPTER:
✓ Network Fundamentals
■ 1.3 Describe the impact of infrastructure components in an enterprise network
■ 1.3.a Firewalls
■ 1.3.b Access points
■ 1.3.c Wireless controllers
■ 1.5 Compare and contrast network topologies
■ 1.5.a Star
■ 1.5.b Mesh
■ 1.5.c Hybrid
Let’s start by defining exactly what an internetwork is: You create an internetwork when you connect two or more networks via a router and configure a logical network addressing scheme with a protocol such as IP or IPv6.
We’ll also dissect the Open Systems Interconnection (OSI) model, and I’ll describe each part of it to you in detail because you really need complete, reliable knowledge of it. Understanding the OSI model is key for the solid foundation you’ll need to build upon with the more advanced Cisco networking knowledge gained as you become increasingly more skilled.
The OSI model has seven hierarchical layers that were developed to enable different networks to communicate reliably between disparate systems. Since this book is centering upon all things CCNA, it’s crucial for you to understand the OSI model as Cisco sees it, so that’s how I’ll be presenting the seven layers to you.
After you finish reading this chapter, you’ll encounter review questions and written labs. These are given to you to really lock the information from this chapter into your memory. So don’t skip them!
Internetworking Basics
Before exploring internetworking models and the OSI model’s specifications, you need to grasp the big picture and the answer to this burning question: Why is it so important to learn Cisco internetworking anyway?
Networks and networking have grown exponentially over the past 20 years, and understandably so. They’ve had to evolve at light speed just to keep up with huge increases in basic, mission-critical user needs (e.g., the simple sharing of data and printers) as well as greater burdens like multimedia remote presentations and conferencing. Unless everyone who needs to share network resources is located in the same office space – an increasingly uncommon situation – the challenge is to connect relevant networks so all users can share the wealth of whatever services and resources are required.
Figure 1.1 shows a basic local area network (LAN) that’s connected using a hub, which is basically just an antiquated device that connects wires together. Keep in mind that a simple network like this would be considered one collision domain and one broadcast domain. No worries if you have no idea what I mean by that because coming up soon, I’m going to talk about collision and broadcast domains enough to make you dream about them!
Figure 1.1 A very basic network
Things really can’t get much simpler than this. And yes, though you can still find this configuration in some home networks, even many of those as well as the smallest business networks are more complicated today. As we move through this book, I’ll just keep building upon this tiny network a bit at a time until we arrive at some really nice, robust, and current network designs – the types that will help you get your certification and a job!
But as I said, we’ll get there one step at a time, so let’s get back to the network shown in Figure 1.1 with this scenario: Bob wants to send Sally a file, and to complete that goal in this kind of network, he’ll simply broadcast that he’s looking for her, which is basically just shouting out over the network. Think of it like this: Bob walks out of his house and yells down a street called Chaos Court in order to contact Sally. This might work if Bob and Sally were the only ones living there, but not so much if it’s crammed with homes and all the others living there are always hollering up and down the street to their neighbors just like Bob. Nope, Chaos Court would absolutely live up to its name, with all those residents going off whenever they felt like it – and believe it or not, our networks actually still work this way to a degree! So, given a choice, would you stay in Chaos Court, or would you pull up stakes and move on over to a nice new modern community called Broadway Lanes, which offers plenty of amenities and room for your home plus future additions all on nice, wide streets
