Router Basics Asso Prof Anan Phonphoem Ph D

Router Basics รศ. ดร. อนนต ผลเพม Asso. Prof. Anan Phonphoem, Ph. D. anan. p@ku. ac. th Intelligent Wireless Network Group (IWING Lab) http: //iwing. cpe. ku. ac. th Computer Engineering Department Kasetsart University, Bangkok, Thailand 1

Router as a Computer n Basic purpose of a router n n Computers that specialize in sending packets over the data network Routers are the network center n generally have 2 connections: n n -WAN connection (Connection to ISP) -LAN connection 2

Router as a Computer n n Data is sent in form of packets between 2 end devices Routers are used to direct packet to its destination 3

Router functions n n examine a packet’s destination IP address find the best path 4

Router (Hardware components) n Router components 5

Router components n n n CPU (Executes operating system instructions) Random access memory (RAM) Read-only memory (ROM) Non-volatile RAM (NVRAM) Flash memory Interfaces (multiple physical interfaces) 6

Internal Components RAM Console Auxiliary NVRAM Flash ROM Interfaces 7

RAM Running copy of configuration file n RAM content is lost on power down n Stores. . . n Routing tables n ARP cache n Fast switching cache n Packet buffering n Packet hold queues n 8

ROM n Contains POST n diagnostic software: Power On Self Test A bootstrap program (loads the Cisco IOS) n And operating system software n Backup, trimmed down version of the IOS n Upgrades require installing new chip set n 9

NVRAM Non-volatile RAM n Stores backup/startup configuration files n n n IP addresses, Routing protocol, Hostname of router Content is not lost when router is powered down or restarted. 10

Flash n EEPROM n Electronically Erasable Programmable Read-Only Memory Holds the Cisco IOS n Allows updating of software without replacing the Flash chip n Store Multiple versions of IOS n Retained on power down n 11

Router Interface n n n a physical connector that enables a router to send or receive packets Each interface connects to a separate network Consist of socket or jack found on the outside of a router Attached to the motherboard or as separate modules Examples of interface types: n Ethernet / fast Ethernet interfaces n Serial interfaces / DSL / ISDN n Management interfaces 12

Major Router Interfaces n LAN Interfaces: n n connect router to LAN network has a layer 2 MAC address can be assigned a Layer 3 IP address usually consist of an RJ-45 jack 13

Major Router Interfaces n WAN Interfaces: n n n connect routers to external networks that interconnect LANs depending on the WAN technology, a layer 2 address may be used. uses a layer 3 IP address 14

Router boot-up process 15

Verify router boot-up process n “show version” n n n n Platform model number Image name & IOS version Bootstrap version stored in ROM Image file name & where it was loaded from Number & type of interfaces Amount of NVRAM Amount of flash Configuration register 16

Using the Router • Understand the Basics of Router's Command Line Interface (CLI). • Demonstrate How to Log into the Router. • Demonstrate How to Enter Router Modes. • Demonstrate Ability to Discern Different Router Modes and Commands 17

Router User Interface 18

User Interface n n n To config: router console user mode—Typical tasks include those that check the router status. In this mode, router configuration changes are not allowed. privileged mode—Typical tasks include those that change the router configuration. 19

User EXEC Modes n User mode (Limited mode) Checking the routers status, looking at routing tables, etc. n You cannot configure the router n Prompt = “>” n Password: Router> Means you’re in user mode 20

Privileged EXEC Modes n Privileged mode Does everything User mode does n Full power to configure the router n In user mode, you enter the command “enable” and then the privileged password n Router> enable Password: Router# Means you’re in privileged mode 21

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Command Lists n To get a list of commands available in either user mode or privileged mode, enter a ? at the prompt. Router> ? Router# ? 23

Getting Help on a Command The ? can be used with a partial command n To use this help feature, enter the partial command, then tap the space bar, then type ? n For example. . . n Router# show ? ip flash: interfaces ipx version parser The Router returned all the available commands for “show” 24

More-- you can continue viewing onto the next available screen by pressing the space bar Typing a question mark (? ) displays a handy list of commonly used commands. 25

To access privileged mode, type enable (or the abbreviation ena). You will be prompted for a password. 26

Use help to check the syntax for setting the clock. The help output shows that the set keyword is required Press Ctrl-P (or the up arrow key) to repeat the previous command entry automatically. The caret symbol (^) and help response indicate an error. To list the correct syntax 27

Error Indicator a carat (^) symbol will indicate where the error occurred. n For example. . . n Router# show runing-config ^ % Invalid input detected at the ‘^’ marker 28

The Show Command 29

Router Status Commands Router#show version Router#show interfaces Router#show flash RAM NVRAM Flash Internetwork Operating System Router#show processes CPU Router#show protocols Tables and Buffers Interfaces Active Programs Configuration File Backup Operating Configuration Systems File Router#show mem Router#show stacks Router#show buffers Router#show running-config Router#write term Router#show startup-config Router#show config 30

Show Commands n show version n show memory n show running-config n show flash n show startup-config n show processes n show interfaces n show protocols n show stacks n show buffers 31

show version 32

Main Topology 33

Routers and the Network Layer n use destination IP address to forward packets n The path a packet takes is determined after a router consults information in the routing table. n After router determines the best path n Packet is encapsulated into a frame n Frame is then placed on network medium in form of Bits 34

Router as a Computer n Routers Operate at Layers 1, 2 & 3 n n Router receives a stream of encoded bits Bits are decoded and passed to layer 2 Router de-encapsulates the frame Remaining packet passed up to layer 3 n n -Routing decision made at this layer by examining destination IP address Packet is then re-encapsulated & sent outbound interface 35

Configure Devices and Apply Addresses n n Implementing Basic Addressing Schemes When designing a new network or mapping an existing network you must provide the following information in the form of a document: n n -Topology drawing that Illustrates physical connectivity Address table that provides the following 36

Configure Devices and Apply Addresses n n Basic Router Configuration A basic router configuration should contain the following: n n -Router name - Host name should be unique -Banner - At a minimum, banner should warn against unauthorized use -Passwords - Use strong passwords -Interface configurations - Specify interface 37

Configure Devices and Apply Addresses 38

Configure Devices and Apply Addresses n Verify Basic Router Configuration n -Issue the show running-config command -Save the basic router configuration by Issuing the copy running-config startupconfig command -Additional commands that will enable you to further verify router configuration are: n n Show running-config - Displays configuration currently in RAM Show startup-config - Displays configuration file 39