Topic3-Part II Modules1-2.pdf

Part II Routing Protocols and Concepts 1 Part II Module 1: WANs and Routers 1.1 WANs 3 4 A CSU/DSU (Channel Service Unit/Data Service Unit) is a digital-interface device used to connect a DTE device, such as a router, to a digital circuit (e.g., a T1 or T3 line). The WIC (WAN Interface Card) may con...

Part II Routing Protocols and Concepts 1 Part II Module 1: WANs and Routers 1.1 WANs 3 4 A CSU/DSU (Channel Service Unit/Data Service Unit) is a digital-interface device used to connect a DTE device, such as a router, to a digital circuit (e.g., a T1 or T3 line). The WIC (WAN Interface Card) may contain an integrated CSU/DSU that can be inserted into a router slot 5 WAN data link protocols describe how frames are carried between systems on a single data link. 6 1.1.3 Router LANs and WANs 7 8 1.2 Routers 9 1.2 Introduction to routers Like a PC RAM Stores routing tables, holds ARP cache, provides temporary memory for the configuration file. Loses content when a router is powered down or restarted NVRAM (Non-Volatile RAM) Provides storage for the startup configuration file Retains content when a router is powered down or restarted Flash Holds the IOS image Retains content when a router is powered down or restarted (IOS: The Internetworking Operating System is a family of proprietary network operating systems used on several router and network switch models manufactured by Cisco Systems) ROM Maintains instructions for power-on self test (POST) diagnostics Stores bootstrap program and basic operating system software Requires replacing pluggable chips on the motherboard for software upgrades Console Provide physical access for initial configuration Interfaces Connect routers to a network for packet entry and exit Can be on the motherboard or on a separate module 10 Router Internal Components 11 Internal Components of a 2600 Router 12 WAN Connections LAN Connections Management Port 13 1.2.4 Management port connections Computer Console connection 14 Modem Connection to Auxiliary Port 15 1.2.5 Console port connections 16 1.2.6 Connecting router LAN interfaces 17 1.2.7 Connecting WAN interfaces 18 Different serial ports 19 Different router connections 20 Part II Module 2: Introduction to Routers 2.1 Operating Cisco IOS Software 22 2.1.1 The purpose of Cisco IOS software As with a computer, a router or switch cannot function without an operating system. The Cisco IOS is the embedded software architecture in all of the Cisco routers and is also the OS of the Catalyst switches. 23 2.1.2 Router user interface The CLI (Command Line Interface) environment can be accessed several ways: 1. Through a console session. 2. Through an AUX port with a modem. 3. To Telnet to the router. Neither of ways 1 and 2 require that the router have any IP services configured. Way 3 requires at least one interface to be configured with an IP address. 24 2.1.3 Router user interface modes 25 2.1.4 Cisco IOS software features IOS Naming Conventions 26 One of the main considerations when selecting a new IOS image is: compatibility with the router flash and RAM memory. In general, the newer the release and the more features that it provides, the more flash and RAM memory it requires. Use show version to check the current image and available flash 27 2.1.5 Operation of Cisco IOS software The Cisco IOS devices have three distinct operating environments or modes: 1. ROM Monitor mode: The ROM monitor performs the bootstrap process and provides low-level functionality and diagnostics. It is used to recover from system failures and to recover a lost password. It can only be accessed by way of a direct, physical connection through the console port. Like safe mode of 2. Boot ROM mode: Windows Only a limited subset of the Cisco IOS feature set is available. It allows write operations to flash memory. It is used primarily to replace the Cisco IOS image that is stored in flash. The Cisco IOS image can be modified in boot ROM with the copy tftp flash command. 3. Cisco IOS mode: The normal operation of most Cisco routers require a copy of the IOS to be loaded into RAM and also executed from RAM. Some IOS images are stored in flash in a compressed format and have to be expanded when copied to RAM. A administrator can use the configuration register setting to control the default startup mode. 28 show version To see the IOS image and version that is running. To see the configuration register setting. show flash To verify that the system has sufficient memory to load a new Cisco IOS image. 29 2.2 Starting a Router 30 2.2.1 Initial startup of Cisco routers POST: oWhen a Cisco router powers up, it performs a power-on self test (POST) to verify the basic operation of the CPU, memory, and network interface ports. Bootstrap: oAfter the POST, the generic bootstrap loader in ROM executes. o A bootstrap is a simple set of instructions that tests hardware and initializes the IOS for operation. Load IOS: oThe IOS can be found in several places. oThe boot field of the configuration register determines the location that is used to load the IOS. Load configuration file: o When the IOS is loaded and operational, the configuration file saved in NVRAM is loaded into main memory and executed one line at a time. oIf no valid configuration file exists in NVRAM, the operating system searches for an available TFTP server. oIf no TFTP server is found, the setup dialog (setup mode) is initiated. oUpon completion of the setup mode, a backup copy of the configuration file may be saved to NVRAM. 31 Setup mode Setup mode is not intended to be used to enter complex protocol features in a router. It is to permit administrators to install a basic configuration for routers. In the setup mode, default answers appear in square brackets [ ] following the question. Press the Enter key to use these defaults. During the setup process, Ctrl-C can be pressed at any time to terminate the process. When Ctrl-C is used to terminate setup, all interfaces are administratively shut down. Like: When you first install Windows. 32 2.2.4 Establish a console session 33 2.2.5 Router login User EXEC mode – Typical tasks include commands that check the status of a router. Privileged EXEC mode –Typical tasks include commands that change the router configuration. Type “enable” to enter privileged mode Type “disable” to exit privileged mode Type “exit” or “end” or press Ctrl-Z to return to privileged mode from configuration mode 34 2.2.6 Keyboard help in the router CLI 35 36 2.2.7 Enhanced editing commands 37 2.2.8 Router command history 38 2.2.9 Troubleshooting command line errors 39