Building a network Data Communications and Computer Networks Lab EP1100 Ezzeldin Shereen Ming Zeng Peiyue Zhao Version 7.0 (2018) Department of Network and Systems Engineering School of Electrical Engineering and Computer Science KTH, Royal Institute of Technology Laboratory Manual 2 Chapter 1 Introduction 1.1 Purpose of the laboratory The main goal of this laboratory is to give you an overview of the different processes involved in building a network, such as a corporate network. You will have to plan the IP address scheme, configure and test the equipment, as well as configure several applications and servers typical of any corporate network (DNS servers for example). After you have completed the laboratory exercises, you should be familiar with the practical issues of the different concepts explained in the course, as well as with the real equipment used nowadays in computer networks. 1.2 Duties before the lab starts Students are required submit the homeworks before the lab starts. Students missing the homework submission will not be accepted to the lab. 1.2.1 Preparatory quizzes Each student has to complete two online lab entry quizzes, which can be found at the course web page. The quizzes are due on the first lab session, and the third. Their purpose is to check that you have enough theoretical knowledge of the tasks that you will perform in the lab. Since these tasks are not part of the course book, you will have to read this manual and its references carefully to pass the quizzes. 1.3 Rules of behavior in the laboratory 1. Every laboratory sessions begins SHARP at the specified time in the schedule. Be on time! Students who arrive later than 15 minutes after the laboratory session had begun will not be accepted to that session. 2. Each lab session is four hours long. Students are welcome to take 10 minutes break during the session when they consider convenient. 3. Please bring your identity cards with you. 4. Students must have their own copies of the laboratory manual. 5. Food and drinks are not allowed inside the laboratory. 6. Please keep your lab position organized and clean, and ensure that the equipment is in the same state (or better) as when you started. 1.4 How to use/read this manual This manual is divided into different chapters and sections. Each chapter corresponds to a logical unit in the lab, like this introduction, and the different lab sessions. The lab sessions have two parts: ’before the lab’ and ’during the lab’. Each of the sessions is self-contained and includes the theory that you will need, either written in this lab manual or as pointers to the proper places to find it. You are required to read both sections carefully and to have a clear idea of the different concepts that you will have to manage while executing the lab tasks. 3 1.5. Notation used in the manual Before the laboratory session: The first thing that you should do is to read the manual completely and start studying the concepts explained in the ‘Before the session’ sections. Your understanding of these concepts will be tested in the homeworks. During the laboratory session: While you are in the lab you must have a copy of the lab manual and your solved homeworks, and perform the different tasks specified. Each of the tasks contains questions that you have to answer. To pass the lab, students must successfully complete all tasks. You must also read this part of the manual before you attend the lab, so that you are familiar with the tasks and their questions. You will not have time to read the manual during the lab! 1.5 Notation used in the manual Whenever an example of syntax is given in the manual, the following conventions apply: • The commands meant to be written in the different terminals, whether it is a router or a PC, are written in bold letters. • Parameters that you have to substitute with their proper values are written in italic. • Parameters inside square brackets are optional and if applied should be written without the square brackets. Example of syntax in this manual: ping [-LRUbdfnqrvVaA] destination Example of issued command: ping -b 255.13.1.0 1.6 Credits Parts of this lab manual have been transcribed literally or with small modifications from the white paper ’Understand- ing IP addresses: everything you ever wanted to know’ by Chuck Semeria ( c 3Com corporation), used with kind permission of 3Com, and from different Linux HOW–TO’s and manuals. Previous versions of this manual were writ- ten/edited by Ignacio Más Ivars, Evgueni Ossipov, Héctor Velayos, Mikael Rudholm, Ognjen Vukovic´ and Ljubica Pajevic.´ Laboratory Manual 4 Chapter 2 Lab Session 1: Building a network Before the session 2.1 Representation of networks in diagrams Network diagrams show the relationship between the elements of communication networks such as computers, periph- eral devices and network equipment. A diagram is the main documentation of a network and its importance cannot be overemphasized. Often, it is the key resource when troubleshooting the network. The network diagram shows how the network operates, so the main task of the network administrator is to maintain the network functioning as its diagram specifies. As a general rule, any modification to the network must first be made to the network diagram, the side effects analyzed and then, if everything works properly, the network equipment will be reconfigured following the new diagram. Despite the fact that there are standards for most of the network parts, the network diagrams are not standardized at all. Developing appropriate network diagrams requires a mixture of experience, knowledge and likely some art. It is a skill that will only be developed through practice, although the study of existing diagrams helps a lot. In these brief notes you will receive some guidelines to interpret network diagrams and then you will practice with the diagram for the lab session. When reading a network diagram, the first thing to dis- cover is the represented layer. As the network diagram shows the relationships between networked elements and these hap- pen at different layers, it is natural that diagrams are classified according to the network layers. The most frequent diagram is the network layer diagram, which shows IP networks and routers between the networks. Usually they are fairly com- plex, so they do not show any information of other network layers. It is important not to overload the diagrams with in- formation, therefore the details of the individual networks are included in link layer network diagrams. This type of dia- grams have a narrower scope (a single sub-network typically) and contains a lot of details about the link and possibly phys- ical layers. Higher level diagrams are also frequent, showing the arrangement of network services like DNS or DHCP, or Figure 2.1: Network symbols often used in network the relationship between application servers and clients. diagrams. Common to all these types of diagrams is the use of sym- bols to represent the different entities. These symbols are not standardized. The diagram author can use any symbols he likes. However, these symbols must be used in a consistent way. This means that both a square and a circle can represent a router, but all routers in the diagram must be represented using the same symbol. In this lab, we will use the symbols in Figure 2.1. Files with these symbols in different formats can be downloaded freely from the Internet (http://www.cisco.com/web/about/ac50/ac47/2.html). The symbols are classified into three categories: network devices, user devices and media. Among the network devices you can find the representation for hubs, switches and routers. The user devices group contains icons for PCs, servers and PCs that act as routers. Finally, the media category contains the symbols for Ethernet connections, serial lines and the cloud. The cloud is a special symbol used to represent parts of the network not shown in a 5 2.2. Equipment description Before the session particular diagram. Thus, it can represent an unspecified network media or whole networks, which is its normal usage. Additional information can be included in the diagram using alphanumeric strings, like IP addresses, host names or device ports. The next section contains some network diagrams that will be used during the lab. At the same time, these diagrams are good examples for the brief notes just introduced. 2.1.1 The network diagram for this session During this lab session you will work with what could be a corporate network of a company with several hundreds of users. The name of the fictitious company is Acme. It has four departments: administration, production, marketing as well as research and development. Each department is divided into four areas, with a Fast Ethernet serving each area. There is a router per area, which connects the Fast Ethernet to the department’s backbone network. The company has four backbones, one per department. All the backbones are connected to the main router of the company, which provides access to the Internet among other services. This network is depicted in Figure 2.2. It is a network level diagram of Acme’s network, containing also the IP addresses used. It is natural that this diagram of a relatively complex network looks confusing at the beginning. Take your time to review it and understand all its data. It will be your guide for troubleshooting the network. As you can see in the figure, the network is quite symmetric. The whole network is called "ACME network", its do- main name is "acme" and it will use the block of IP addresses from 192.168.0.0 to 192.168.0.255 (i.e.