Introduction to Routing and Packet Forwardin g g Routing Protocols and Concepts – Chapter 1 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public ITE PC v4.0 Chapter 1 1 Objectives  I de ntif y a r ou t e r as a co m pu t e r with a n OS a n d de y a ou e as a co pu e a OS a d hardware designed for the routing process.  Demonstrate the ability to configure devices and Demonstrate the ability to configure devices and apply addresses.  Describe the structure of a routing table Describe the structure of a routing table .  Describe how a router determines a path and switches packets switches packets ITE PC v4.0 Chapter 1 2 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public Router as a Computer  D esc ri be th e bas i c pu r pose o f a r ou t er esc be e bas c pu pose o a ou e -Computers that specialize in sending packets over the data network. They are responsible for interconnecting networks by selecting the best path for a packet to travel and forwarding packets to their destination  Routers have many of the same hardware and software com p onents that are found in other com p uters pp including: –CPU –RAM –ROM ITE PC v4.0 Chapter 1 3 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public – Operating System Router as a Computer  Router com p onents and their functions” p CPU - Executes operating system instructions  such as system initialization, routing functions, and switching functions.  Random access memory (RAM) RAM stores the instructions and data needed  Random access memory (RAM) - RAM stores the instructions and data needed to be executed by the CPU. RAM is used to store these components: –Operating System: The Cisco IOS (Internetwork Operating System) is copied into RAM durin g bootu p . gp –Running Configuration File: This is the configuration file that stores the configuration commands that the router IOS is currently using. – IP Routin g Table: This file stores information about directl y connected and g y remote networks. It is used to determine the best path to forward the packet. –ARP Cache: This cache contains the IPv4 address to MAC address mappings, similar to the ARP cache on a PC. The ARP cache is used on hh LANi f h Eh i f routers t h at h ave LAN i nter f aces suc h as E t h ernet i nter f aces. –Packet Buffer: Packets are temporarily stored in a buffer when received on an interface or before they exit an interface. ITE PC v4.0 Chapter 1 4 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public RAM is volatile memory and loses its content when the router is powered down or restarted. Router as a Computer  R ou t e r co m po n e nt s a n d th e ir f u n c ti o n s ” ouecopoesadeucos Read-only memory (ROM) - Holds diagnostic software used when router is powered up. Stores the router’s bootstrap p ro g ram. pg –ROM is a form of permanent storage. Cisco devices use ROM to store: –The bootstrap instructions –Basic diagnostic software – Scaled - down version of IOS – Scaled - down version of IOS ROM uses firmware, which is software that is embedded inside the integrated circuit. – Firmware includes the software that does not normally need to be modified or upgraded, such as the bootup instructions. – ROM does not lose its contents when the router loses power ITE PC v4.0 Chapter 1 5 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public or is restarted. Rt C t R ou t er as a C ompu t e r  Router components and their functions” Non-volatile RAM (NVRAM) - Stores startup configuration. This may include IP addresses (Routing protocol Hostname of router) addresses (Routing protocol , Hostname of router) NVRAM (Nonvolatile RAM) does not lose its information when power is turned off. This is in contrast to the most common forms of RAM, such as DRAM, that requires continual power to maintain its information.  NVRAM is used by the Cisco IOS as permanent storage for the startup configuration file  NVRAM is used by the Cisco IOS as permanent storage for the startup configuration file . All configuration changes are stored in the running-config file in RAM, and with few exceptions, are implemented immediately by the IOS. To save those changes in case the router is restarted or loses power, the running-config must be copied to NVRAM where it is stored as the startup - config file NVRAM retains its must be copied to NVRAM , where it is stored as the startup - config file . NVRAM retains its contents even when the router reloads or is powered off. Flash memory - Contains the operating system (Cisco IOS) In most models of Cisco routers, the IOS is permanently stored in flash memory and copied into RAM during the bootup process, where it is then executed by the CPU. Flash consists of SIMMs or PCMCIA cards, which can be upgraded to increase the amount of flash memory increase the amount of flash memory . Interfaces - There exist multiple physical interfaces that are used to connect network. Examples of interface types: -Ethernet / fast Ethernet interfaces ITE PC v4.0 Chapter 1 6 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public -Serial interfaces -Management interfaces Router as a Computer  R ou t e r co m po n e nt s ou e co po e s ITE PC v4.0 Chapter 1 7 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public Internetwork Operating System  The operating system software used in Cisco routers is known as Cisco Internetwork Operating System (IOS) Internetwork Operating System (IOS) . – Cisco IOS is a multitasking operating system that is integrated with routing, switching, internetworking, and telecommunications functions.  Although the Cisco IOS may appear to be the same on many routers, Although the Cisco IOS may appear to be the same on many routers, there are many different IOS images. – An IOS image is a file that contains the entire IOS for that router. Cisco creates many different types of IOS images, depending upon the model of the router and the features within the IOS. the router and the features within the IOS. – Typically the more features in the IOS, the larger the IOS image, and therefore, the more flash and RAM that is required to store and load the IOS.  Although some routers provide a graphical user interface (GUI), the dli i t f (CLI)i h th d f comman d li ne i n t er f ace (CLI) i s a muc h more common me th o d o f configuring Cisco routers. – The CLI is used throughout this curriculum.  Upon bootup the startup config file in NVRAM is copied into RAM and  Upon bootup , the startup - config file in NVRAM is copied into RAM and stored as the running-config file. – IOS executes the configuration commands in the running-config. Any changes entered by the network administrator are stored in the running- config and are immediately implemented by the IOS ITE PC v4.0 Chapter 1 8 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public config and are immediately implemented by the IOS . Overview - Managing Cisco IOS Software (cont) Overview Managing Cisco IOS Software (cont) ITE PC v4.0 Chapter 1 9 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public Router as a Computer  M ajo r p h ases t o th e ajo p ases o e router boot-up process Test router hardware Power-On Self Test (POST) Execute bootstra p loade r p Locate & load Cisco IOS software Locate IOS - Locate IOS -Load IOS Locate & load startup configuration file or enter setup mode -Bootstra p p ro g ram looks ITE PC v4.0 Chapter 1 10 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public pp g for configuration file [...]... config-register ITE PC v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 21 Configuration register: 0, 1, and 2 and above ITE PC v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 22 Configuration register: 210 2 and 214 2 ITE PC v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 23 Configuration register 1 Router(config)#config-register... v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 11 Router R t as a C Computer t Major phases to the router boot-up process ITE PC v4.0 Chapter 1 Step 1 and 2: Test router hardware •Power-On Self Test (POST) P O S lf T t –During this self-test, the router executes diagnostics from ROM on several hardware components including the CPU, RAM, and NVRAM •Execute bootstrap loader –The... b command at the ROM monitor prompt To configure the system to boot automatically from ROM ROM, set the configuration register to 0xnnn1, This value sets the boot field bits to 00 01 binary To configure the system to use the boot system commands in NVRAM set the configuration register to NVRAM, any value from 0xnnn2 to 0xnnnF, These values set the boot field bits to a value between 0 010 and 11 11 binary... (C2600-I-M), V i 12 .2(28), (C2600 I M) Version 12 2(28) RELEASE SOFTWARE (fc5) Bootstrap version stored in ROM ROM: System Bootstrap, O S Version 12 .1( 3r)T2, RELEASE SOFTWARE (fc1) Image file name & where it was loaded from System image file is "flash:c2600-i-mz 12 2-28 bin" flash:c2600 i mz .12 2 28.bin ITE PC v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 15 Router as a Computer... flash 16 384K bytes of processor board System flash (Read/Write) This is the amount of flash memory on the router Flash is used to permanently store the Cisco IOS ITE PC v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 17 Router as a Computer show version Configuration register Configuration register is 0x 210 2 ITE PC v4.0 Chapter 1 –The last line of the show version command displays... value 2 3 ITE PC v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 24 Stages of the router power-on boot sequence 1 ROM 1, 2 1 POST 2 Bootstrap code executed 3 Check Configuration Register value (NVRAM) 3 0 = ROM Monitor mode 1 = ROM IOS 2 - 15 = Boot system from flash 4 2 Check for IOS boot system commands in startup-config file (NVRAM) If boot system commands in startup-config... numbers In this example, the Cisco 26 21 router has 60, 416 KB (kilobytes) of free DRAM used for temporarily storing the Cisco IOS y processes The and other system p other 5 ,12 0 KB is dedicated for packet memory The sum of these numbers is 65,536K, or 64 megabytes (MB) of total DRAM ITE PC v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 16 Router as a Computer show version Verify... interfaces i t f –Each interface has a Layer 3 IP address and subnet mask that configures it for a different network –The Ethernet interfaces also have Layer 2 Ethernet MAC addresses The WAN interfaces are using different Layer 2 encapsulations –Serial 0/0/0 is using HDLC S C –Serial 0/0 /1 is using PPP –Both of these serial point-to-point Both point to point protocols use a broadcast address for the Layer 2... register form the boot field To ensure that the upper 12 bits are not changed, first retrieve the current values of the configuration register using the show version command Then use the config-register command, changing only the value of the last hexadecimal digit ITE PC v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 19 Configuration register (cont.) (cont ) To enter the... bootstrap program is to locate the Cisco IOS and load it into RAM –Note: At this point, if you have a console connection to the router, you will begin to see output on the screen Step 3 and 4: Locate & load Cisco IOS software -Locate IOS and Load IOS Locate –The IOS is typically stored in flash memory, but can also be stored in other places such as a TFTP server –If a full IOS image can not be located, . Introduction to Routing and Packet Forwardin g g Routing Protocols and Concepts – Chapter 1 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public ITE PC v4.0 Chapter 1 1 Objectives  I de ntif y . between 0 010 and 11 11 binary. Using boot system commands in NVRAM is the default. Check Configuration Register value (NVRAM) 0 = ROM Monitor mode 1 = ROM IOS ITE PC v4.0 Chapter 1 20 © 2007. ITE PC v4.0 Chapter 1 10 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public pp g for configuration file Stages of the router power-on boot sequence ITE PC v4.0 Chapter 1 11 © 2007 Cisco