Router Components

1
Router Components

• Semester 2
• Chapter 4

Instructor Mehran Dowlatshahi
2
Table of Contents

• More on Components
• The Show Command
• Network Neighbor Routers
• Basic Network Testing

3
More on Components

• Configuration
• Details on RAM
• Router Modes

Table of Contents
4
External Configuration

• A router can be configured from four separate
  sources
• Console port (used to initially configure the
  router)
• WAN/LAN links (attach through hub or switch using
  a patch cable)
• Auxiliary port (needs a modem)
• TFTP server installed on the network
• The easiest place to configure from is the
  console port.
• Attach a rollover cable from the router to your
  computer COM1 or COM2 port
• Open HyperTerminal to log in

5
Internal Configuration

• Review Router Basics section in Ch.2/3
  Powerpoint.

6
RAM Specifics
As the router is booted, the following is loaded
into RAMs Working Storage.
Command Executive
Internetwork Operating System (IOS)
RAM
Programs
Active Config File
Tables
Buffers
7
RAM Specifics

• Programs include the bootstrap program that
• tests the equipment (POST)
• and locates the IOS.

Programs
8
RAM Specifics
Once the IOS is located by the bootstrap program,
it is loaded in to RAM.
Internetwork Operating System (IOS)
Programs
9
RAM Specifics
Part of the IOS is the Command EXEC. This is the
program that translates the commands you type
into a language that the IOS can understand.
Command Executive
Internetwork Operating System (IOS)
Programs
10
RAM Specifics
Once the IOS is initialized, it looks for an
active configurations file (usually in NVRAM) and
loads it. This file tells the router
specifically what to do.
Command Executive
Internetwork Operating System (IOS)
Programs
Active Config File
11
RAM Specifics

• The tables are loaded from the configuration file
  including...
• ARP Tables
• Routing Tables

Command Executive
Internetwork Operating System (IOS)
Programs
Active Config File
Tables
12
RAM Specifics
Finally, all leftover memory in RAM is used as
the buffer for processing incoming and outgoing
packets.
Command Executive
Internetwork Operating System (IOS)
Programs
Active Config File
Tables
Buffers
13
Router Modes
Good graphic. Learn it.
14
The Show Command
Table of Contents
15
Router Status Commands

• On the next slide, you will see a graphic
  displaying the most common show commands.
• Be sure to copy this graphic in your notes.
• You need to know which component of the router
  the show command accesses and what each show
  command displays.

16
Flash
NVRAM
RAM
Internetwork Operating System
Backup Configuration File
Operating Systems
Interfaces
Programs
Active Configuration File
Tables and Buffers
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Show Commands Defined

• show version -- displays the configuration of the
  system hardware, the software version, the names
  and sources of configuration files, and the boot
  image
• show startup-config (show config on Cisco IOS
  10.3 or earlier) -- displays the backup
  configuration file
• show flash -- shows information about the Flash
  memory device
• show interfaces -- displays statistics for all
  interfaces configured on the router
• show processes -- displays information about the
  active processes
• show protocols -- displays the configured
  protocols shows the status of all configured
  Layer 3 protocols

18
Show Commands Defined

• show running-config (write term on Cisco IOS 10.3
  or earlier) -- displays the active configuration
  file
• show memory -- shows statistics about the
  router's memory, including memory free pool
  statistics
• show stacks -- monitors the stack use of
  processes and interrupt routines and displays the
  reason for the last system reboot
• show buffers -- provides statistics for the
  buffer pools on the router

19
Lab

• Before moving on, make sure you have completed
• Lab 4.2.4-Router show commands

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Network Neighbor Routers
Table of Contents
21
CDP

• In order to fully understand how Cisco Discovery
  Protocol operates, do the lab.
• 4.3.5-CDP Neighbors

22
Basic Network Testing
Table of Contents
23
Multiple Testing Methods

• For a basic introduction to router
  troubleshooting, do the labs.
• 4.4.2-Remote telnet access
• 4.4.3-ICMP Ping
• 4.4.4-Traceroute command
• 4.4.7-Show interfaces clear counters
• 4.5.1-Troubleshooting tools challenge
• Active mental participation in answering lab
  questions is crucial to do well on the test.
• You will also retain the knowledge longer if you
  think about what you are doing and why!