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By Muhammad Asghar Khan
07 - Installing & Operating Cisco LAN Switches
Reference: Cisco CCENT/CCNA ICND1 100-101 Official Cert Guide By WENDELL ODOM
© Cisco Press
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Agenda
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IntroductionCisco Catalyst Switch BrandCisco Linksys Switch Brand
The Cisco Catalyst 2960 SwitchSwitch Status from LEDs
Accessing the Cisco IOS CLICLI Access from the ConsoleCLI Access with Telnet & SSHSetting Password Security for CLI
Cisco IOS Modes of OperationUser EXEC ModePrivileged EXEC Mode
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Agenda
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Global Configuration Mode
Switch Configuration FilesTypes of Switch Memory
RAM/DRAM ROM Flash Memory NVRAM
Types of Configurations Initial Configuration (Setup Mode) Startup Configuration Running Configuration
Copying Configuration FilesErasing Configuration Files
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Introduction
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Cisco has two major brands of LAN switching productsCisco Catalyst Switch Brand
Includes a large collection of switches, all of which have been designed with Enterprises in mind
The Catalyst switches have a wide range of sizes, functions, and forwarding rates
Cisco Linksys Switch Brand Includes a variety of switches designed for use in the home
The CCNA exams focus on how to implement LANs using Cisco Catalyst switches
Both the Catalyst and Linksys brands of Cisco switches provide the same base features
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Introduction
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Within the Cisco Catalyst brand, Cisco produces a wide variety of switch series or families
Each switch series includes several specific models of switches that have:Similar Features, Similar Price-Versus-Performance trade-offs, andSimilar Internal components
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The Cisco Catalyst 2960 Switch
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Cisco positions the 2960 series/family of switches as full-featured, low cost wiring closet/cabinet switches for enterprises
2960 switches are mostly used as access switches
The distribution layer switches are often from a different Cisco switch family, typically a more powerful and more expensive product family
Figure on next slide shows the photo of the 2960 switch series from Cisco; each switch is a different specific model of switch inside the 2960 series
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The Cisco Catalyst 2960 Switch
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Cisco Catalyst 2960 Series
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The Cisco Catalyst 2960 Switch
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Three of the five switches have 48 RJ-45 10/100 ports, meaning that these ports can negotiate the use of 10BASE-T or 100BASE-TX Ethernet
These switches also have few additional RJ-45 ports on the right that are 10/100/1000 interfaces on the right, intended to connect to the core switches of an Enterprise campus LAN
Cisco refers to a switch’s physical connectors as either interfaces or ports. Each interface has a number in the style x/y, where x and y are two different numbers
In a 2960, the number before the / is always 0. The first 10/100 interface on a 2960 is numbered starting at 0/1, the second is 0/2, and so on
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The Cisco Catalyst 2960 Switch
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The interfaces also have names; for example, “interface FastEthernet 0/1” is the first of the 10/100 interfaces
Any Gigabit-capable interfaces would be called “GigabitEthernet” interfaces
Cisco supports two major types of switch operating systems: Internetwork Operating System (IOS) Catalyst Operating System (Cat OS)
Most Cisco Catalyst switch series today run only Cisco IOS But for some historical reasons, some of the high-end Cisco
LAN switches support both Cisco IOS and Cat OS Cisco also uses the term hybrid to refer to 6500 switches
that use Cat OS and the term native to refer to 6500 switches that use Cisco IOS
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The Cisco Catalyst 2960 Switch
www.asghars.blogspot.com
Switch Status from LEDsSwitch hardware includes several LEDs that
provide some status and troubleshooting information
Figure shows the front of a 2960 series switch, with five LEDs on the left, one LED over each port, and a mode button
SYST (System)
RPS (Redundant Power Supply)STAT (Status)
DUPLX (Duplex)SPEED
Port
MODE
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The Cisco Catalyst 2960 Switch
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To make sense of the LEDs, consider the specific example of SYST LED SYST LED provides a quick overall status of the switch,
with three states on most 2960 switch models: Off: switch is not powered on On (green): switch is powered on and operational (Cisco
IOS has been loaded) On (amber): switch’s Power-On Self Test (POST) process
failed, and the Cisco IOS did not load. In this case, the typical response is to power the switch off and back on again. If the same failure occurs, a call to the Cisco Technical Assistance Center (TAC) is typically the next step
The particular details of how each LED works differ between different Cisco switch families and with different models inside the same switch family
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The Cisco Catalyst 2960 Switch
www.asghars.blogspot.com
The port LEDs—the LEDs sitting above or below each Ethernet port—means something different depending on which of three port LED modes is currently used on the switch
The switches have a mode button (labeled with number 6 in Figure) that, when pressed, cycles the port LEDs through three modes: STATDUPLX, and SPEED
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The Cisco Catalyst 2960 Switch
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Each of the three port LED modes changes the meaning of the port LEDs associated with each port In STAT (status) Mode
Off: The link is not workingSolid Green: The link is working, but there’s no current
trafficFlashing Green: The link is working, and traffic is currently
passing over the interfaceFlashing Amber: The interface is administratively disabled
or has been dynamically disabled for a variety of reasons In SPEED Mode
Dark LED; meaning 10 MbpsSolid Green Light; meaning 100 Mbps Flashing Green; meaning 1000 Mbps (1 Gbps)
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Accessing the Cisco IOS CLI
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The command-line interface (CLI) is a text-based interface in which the user, typically a network engineer, enters a text command and presses Enter
Pressing Enter sends the command to the switch, which tells the device to do something
Cisco IOS not also define an interface (CLI) for humans but it also controls the switch’s performance and behavior
The switch CLI can be accessed through three popular methods—the console, Telnet, and Secure Shell (SSH)
The console is a physical port built specifically to allow access to the CLI
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Accessing the Cisco IOS CLI
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Telnet and SSH use the IP network in which the switch resides to reach the switch
Figure on next slide shows the cabling
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Accessing the Cisco IOS CLI
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Next, a terminal emulator software package (e.g. tera term) must be installed and configured to use the PC’s serial port, matching the switch’s console port settings
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Accessing the Cisco IOS CLI
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The default console port settings on a switch are as
follows: 9600 bits/second No hardware flow control 8-bit ASCII No stop bits 1 parity bit
Figure shows the configuration window for the settings just listed
CLI Access with Telnet & SSHMost terminal emulator packages also include both
Telnet & SSH client functions
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Accessing the Cisco IOS CLI
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Telnet or SSH application protocol calls the terminal emulator a “Telnet Client or SSH Client” and device that listens for commands is called “Telnet Server or SSH Server”
The switch runs Telnet and SSH server software by default, but needs to have an IP address configured
Telnet & SHH is TCP based where Telnet uses the port 23 and SHH uses the port 22
The key difference b/w Telnet & SHH is that Telnet sends all data as clear-text data, while the SHH sends data in more secure manner by using the encryption
By default switch allows only console access, but no Telnet or SHH access
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Accessing the Cisco IOS CLI
www.asghars.blogspot.com
Cisco switches refers to console as console line-specifically, console line 0
Cisco switches also support 16 Telnet sessions, referenced as virtual terminal (vty) lines 0 through 15
SSH requires a little more effort than console & Telnet, as SSH uses public key cryptography to exchange a shared session key
Additionally, SSH requires both username and password for login
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Cisco IOS Modes of Operation
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Cisco IOS provides access to several different command modes
Each command mode provides a different group of related commands
Entering a question mark (?) at the system prompt allows you to obtain a list of commands available for each command mode
The three basic modes are:User EXEC ModePrivileged EXEC ModeGlobal Configuration Mode
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Cisco IOS Modes of Operation
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User EXEC ModeIt is the default command mode for the CLI It is also called User ModeThe user EXEC commands allow you to connect
to remote devices, change terminal settings on a temporary basis, perform basic tests, and list system information
EXEC refers to the fact that the user only enter the command, switch executes that command and then display the message
The prompt for user EXEC mode is the name of the device followed by an angle bracket:
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Cisco IOS Modes of Operation
www.asghars.blogspot.com
Privileged EXEC ModePrivileged EXEC commands set operating parametersPrivileged EXEC mode is password protected It is also called simply privileged or enable modeTo enter privileged mode, enter the ”enable” EXEC
command from user EXEC mode:
To set enable mode password, use either the ”enable password” or ”enable secret” commands
It is recommended that you use the ”enable secret” command because it uses an improved encryption algorithm
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Cisco IOS Modes of Operation
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Use the ”enable password” command only if you boot an older image of the Cisco IOS software
Figure shows the User & Privileged modes
Global Configuration ModeGlobal configuration commands apply to features
that affect the system as a whole, rather than just one protocol or interface
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Cisco IOS Modes of Operation
www.asghars.blogspot.com
Commands entered in configuration mode update the active configuration file
Configuration mode itself contains submodesSubmodes used to configure specific system featuresContext-setting commands move you from one
configuration mode or context to anotherTo enter global configuration mode, enter
the ”configure” command from privileged EXEC mode:
The system prompt changes to indicate that you are now in global configuration mode
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Cisco IOS Modes of Operation
www.asghars.blogspot.com
Some of the sub-modes are:Access-list ConfigurationLine Configuration Interface Configuration
Access-list ConfigurationUse access-list configuration mode when you are
creating a named IP or IPX access listFrom global configuration mode, use the “ip access-list” or “ipx access-list” command
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Cisco IOS Modes of Operation
www.asghars.blogspot.com
Line configurationLine configuration commands modify the operation of
an auxiliary, console, physical, or virtual terminal lineFrom global configuration mode, enter by specifying
a line with a line {aux|con|tty|vty} line-number [ending-line-number] command
Interface ConfigurationThe commands entered in this mode modify the
operation of an interface From global configuration mode, enter by specifying
an interface with an interface command
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Cisco IOS Modes of Operation
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Figure shows the relationship b/w EXEC modes and configuration mode
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Cisco IOS Modes of Operation
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The end or Ctrl+z key sequence exit the user from any part of configuration mode and go back to privileged EXEC mode
While the exit command backs you out of configuration mode one sub-configuration mode at a time
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Switch Configuration Files
www.asghars.blogspot.com
To work with files, you need some sort of memory Cisco switches uses several types of permanent memory
as:RAM/DRAM
Used by switch as it is used by any other computerROM
Stores bootstrap/boot-helper program, that is loaded when the switch first power on
Bootstrap program finds the image of IOS and load it into the RAM
Flash Memory Found in the form of chip inside the switch or a removable
memory card Stores the Cisco IOS images and it is the default location where
bootstrap searches for the IOS image
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Switch Configuration Files
www.asghars.blogspot.com
It can also be used to store configuration or backup filesNonvolatile RAM (NVRAM)
Stores the initial or startup configuration file
A configuration file saves the switch configuration commands in text format
Switch maintains the following types of configuration: Initial Configuration (Setup Mode)
Setup mode leads a switch administrator to a basic switch configuration by using questions that prompt for basic switch configuration parameters
Figure on next slide describe the process used by setup mode
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Switch Configuration Files
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Startup ConfigurationUsed for initialization when the switch boots If this file does not exist, the system boots using
the factory defaults
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Switch Configuration Files
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It is stored in NVRAMYou can use the show startup-config command to view
the startup configuration fileThe IOS File System (IFS) refers to startup-config as
nvram:startup-configRunning Configuration
Stores the currently used configuration commandsThis file changes dynamically when someone enters
commands in configuration mode It is stored in RAM If the switch is reloaded (rebooted) and the running
configuration is not saved all commands will be lostYou can use the show running-config command to view
the startup configuration file
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Switch Configuration Files
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The IOS File System (IFS)
refers to running-config
as system:running-config
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Switch Configuration Files
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Copying Configuration FilesThe “copy” command can be used to copy files
b/w RAM or NVRAM on a switch and a TFTP serverThe copy command can be summarized as:
copy { tftp|running-config|startup-config }
{ tftp|running-config|startup-config }
It always replaces the existing configuration file when the file is copied into NVRAM or into a TFTP server, while it merged the configuration file into the running-config file in RAM
Figure on next slide depicts the locations and results of copy operation
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Switch Configuration Files
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Erasing Configuration FilesYou can use three different commands to erase
the contents of NVRAMwrite erase (older)erase startup-config (older)erase nvram (recomened)
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Switch Configuration Files
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All the three commands will erase the contents of the NVRAM configuration file
Note there is no command to erase the contents of the running-config file; to clear the running-config file, simply erase the startup-config file and then “reload” the switch
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