CCNA :) Be a Good Network Administrator

Summary This page summarizes the topics discussed in this module. The major difference between a WAN and a LAN is the geographical area that is covered. A LAN connects workstations, printers, servers, and other devices within a building or other small area. A WAN is used to connect multiple LANs, typically over a large geographical area. The primary characteristics of a WAN include the ability to connect devices separated by wide geographical areas, the use of service companies to make these connections, and the serial connections used to access bandwidth. There are several organizations that define and manage the standards used for WAN design such as ITU-T, ISO, IETF, and EIA. WANs operate at the physical layer and the data link layer, which are Layers 1 and 2 of the OSI reference model. The devices used in a WAN, such as routers, CSU/DSUs, modems, and communication servers, operate at the physical layer. At the data link layer, the protocols determine how frames are carried b...

Connecting WAN interfaces 1.2.7 This page discusses the different forms of WAN connections. A WAN uses many different technologies to make data connections across a broad geographic area. WAN communication services are usually leased from service providers. WAN connection types include leased line, circuit-switched, and packet-switched. For each type of WAN service, the customer premises equipment (CPE), which is often a router, is the DTE. This is connected to the service provider through a DCE device, which is commonly a modem or CSU/DSU. This device is used to convert the data from the DTE into a form acceptable to the WAN service provider. Perhaps the most commonly used router interfaces for WAN services are serial interfaces. Answer the following questions to select the proper serial cable: • What is the type of connection to the Cisco device? Cisco routers may use different connectors for the serial interfaces. The interface on the left is a Smart Serial interface. The ...

Console port connections 1.2.5 This page will provide more information about the console port. The console port is a management port that is used to provide out-of-band access to a router. It is used to set up the initial configuration of a router and to monitor it. The console port is also used for disaster recovery procedures. A rollover cable and an RJ-45 to DB-9 adapter are used to connect a PC to the console port. Cisco supplies the necessary adapter to connect to the console port. The PC or terminal must support VT100 terminal emulation. Terminal emulation software such as HyperTerminal is usually used. The following are steps to connect a PC to a router: 1. Configure terminal emulation software on the PC for the following: • The appropriate COM port • 9600 baud • 8 data bits • No parity • 1 stop bit • No flow control 2. Connect the RJ-45 connector of the rollover cable to the router console port. 3. Connect the other end of the rollover cable to the RJ-45 ...

Management port connections 1.2.4 This page will introduce the console and auxiliary (AUX) ports, which are also known as the management ports. These asynchronous serial ports are not designed as networking ports. The console port is required for the configuration of the router. Not all routers have an auxiliary port. When the router is first put into service, there are no networking parameters configured. Therefore the router cannot communicate with any network. To prepare for initial startup and configuration, attach an RS-232 ASCII terminal, or attach the rollover cable to a personal computer running terminal emulating software such as HyperTerminal, to the system console port. Then configuration commands can be entered to set up the router. After the initial configuration is entered into the router through the console or auxiliary port, the router can be connected to the network to troubleshoot or monitor it. The router can also be remotely configured through the configurat...

Router physical characteristics 1.2.2 This page will help students identify the location of different components on a router. It is not critical to know the location of the physical components inside the router to understand how to use the router. However in some situations, such as adding memory, it can be very helpful. The exact components used and their location varies between router models. Figure identifies the internal components of a 2600 router. Figure shows some of the external connectors on a 2600 router. The next page will describe the external connections on a router. Router external connections 1.2.3 This page will describe the three basic types of connections on a router, which are LAN interfaces, WAN interfaces, and management ports. LAN interfaces allow routers to connect to the LAN media. This is usually some form of Ethernet. However, it could be some other LAN technology such as Token Ring or FDDI. WANs provide connections through a service provider...

Introduction to WANs 1.2.1 While the exact architecture of the router varies between router models, this page will introduce the major internal components. Figures and show the internal components of some of the Cisco router models. The common components are covered in the paragraphs below. CPU – The Central Processing Unit (CPU) executes instructions in the operating system. Among these functions are system initialization, routing functions, and network interface control. The CPU is a microprocessor. Large routers may have multiple CPUs. RAM – RAM is used for routing table information, fast switching caches, running configurations, and packet queues. In most routers the RAM provides run time space for executable Cisco IOS software and its subsystems. RAM is usually logically divided into main processor memory and shared input/output (I/O) memory. Shared I/O memory is shared among interfaces for temporary storage of packets. The contents of RAM are lost when power is removed. RAM...

Academy approach to hands-on labs 1.1.5 This page will help students understand how a lab is configured to simulate a WAN. In the academy lab, all the networks will be connected with serial or Ethernet cables and the students can see and physically touch all the equipment. Unlike the academy lab setup, the serial cables in the real world are not connected back to back. In a real world situation, one router could be in New York, while another router could be in Sydney, Australia. An administrator located in Sydney would have to connect to the router in New York through the WAN cloud in order to troubleshoot the New York router. In the academy lab, devices that make up the WAN cloud are simulated by the connection between the back-to-back DTE-DCE cables. The connection from one router interface s0/0 to another router interface s0/1 simulates the whole circuit cloud. This page concludes the discussion about WANs. The next lesson will describe routers in greater detail.

Role of routers in a WAN 1.1.4 This page will review WANs in relation to the OSI model and explain the functions of a router. The standards and protocols or primary functions of a WAN operate at the physical layer and at the data link layer. This does not mean that the other five layers of the OSI model are not found in a WAN. It simply means that the standards and protocols that define a WAN connection are typically found at the physical and data link layers. In other words, the Layer 1 and Layer 2 WAN standards and protocols are different than the Layer 1 and Layer 2 LAN standards and protocols. The WAN physical layer describes the interface between the data terminal equipment (DTE) and the data circuit-terminating equipment (DCE). Generally, the DCE is the service provider and the DTE is the attached device. In this model, the services offered to the DTE are made available through a modem or a CSU/DSU. The main function of a router is to transmit data using Layer 3 addresses...

Router LANs and WANs 1.1.3 Routers can be used to segment LANs, but they are mainly used as WAN devices. This page will explain how routers are used in a network. Routers have both LAN and WAN interfaces. WAN technologies are frequently used to connect routers. Routers use WAN connections to communicate with each other. Routers are the backbone devices of large intranets and of the Internet. They operate at Layer 3 of the OSI model, making decisions based on network addresses. The two main functions of a router are to select the best path for packets and to route packets to the proper interface. To accomplish this, routers build routing tables and exchange network information with other routers. An administrator can configure static routes to maintain routing tables. However, most routing tables are maintained dynamically through the use of a routing protocol that exchanges network topology information with other routers. For example, if Computer X needs to communicate with Com...

Introduction to routers in a WAN 1.1.2 This page will provide a brief review of routers. A router is a special type of computer. It has the same basic components as a standard desktop PC. It has a CPU, memory, a system bus, and various input/output interfaces. However, routers are designed to perform some very specific functions that are not typically performed by desktop computers. For example, routers connect and allow communication between two networks and determine the best path for data to travel through the connected networks. Just as computers need operating systems to run software applications, routers need the Internetwork Operating System (IOS) software to run configuration files. These configuration files contain the instructions and parameters that control the flow of traffic in and out of the routers. Routers use routing protocols to determine the best path for packets. The configuration file specifies all the information for the correct setup and use of the selected...

This page will provide a brief review of routers. A router is a special type of computer. It has the same basic components as a standard desktop PC. It has a CPU, memory, a system bus, and various input/output interfaces. However, routers are designed to perform some very specific functions that are not typically performed by desktop computers. For example, routers connect and allow communication between two networks and determine the best path for data to travel through the connected networks. Just as computers need operating systems to run software applications, routers need the Internetwork Operating System (IOS) software to run configuration files. These configuration files contain the instructions and parameters that control the flow of traffic in and out of the routers. Routers use routing protocols to determine the best path for packets. The configuration file specifies all the information for the correct setup and use of the selected, or enabled, routing and routed proto...