Basic Switch configuration

Basic Switch configurationBasic Switch configuration

W.lilakiatsakunW.lilakiatsakun

Command Syntax (1)Command Syntax (1)

Command Syntax (2)Command Syntax (2)

Context Sensitive HelpContext Sensitive Help

Console Error MessageConsole Error Message

Boot sequence (1)Boot sequence (1)

• The switch loads the The switch loads the boot loader softwareboot loader software. The . The boot loader is a small program stored in boot loader is a small program stored in NVRAM and is run when the switch is first NVRAM and is run when the switch is first turned on.turned on.

• The boot loader:The boot loader:– Performs Performs low-level CPU initializationlow-level CPU initialization. It initializes the . It initializes the

CPU registers, which control where physical memory CPU registers, which control where physical memory is mapped, the quantity of memory, and its speed. is mapped, the quantity of memory, and its speed.

– Performs Performs power-on self-test (POST)power-on self-test (POST) for the CPU for the CPU subsystem. It tests the CPU DRAM and the portion of subsystem. It tests the CPU DRAM and the portion of the flash device that makes up the flash file system. the flash device that makes up the flash file system.

Boot sequence (2)Boot sequence (2)

– Initializes the flash file systemInitializes the flash file system on the system board. on the system board. – Loads a default operating system software imageLoads a default operating system software image into into

memory and boots the switch. The boot loader finds memory and boots the switch. The boot loader finds the Cisco IOS image on the switch by first looking in a the Cisco IOS image on the switch by first looking in a directory that has the same name as the image file directory that has the same name as the image file (excluding the .bin extension). (excluding the .bin extension). • If it does not find it there, the boot loader software searches If it does not find it there, the boot loader software searches

each subdirectory before continuing the search in the original each subdirectory before continuing the search in the original directory.directory.

• The operating system then initializes the The operating system then initializes the interfaces using the Cisco IOS commands found interfaces using the Cisco IOS commands found in the operating system configuration file, in the operating system configuration file, config.textconfig.text, stored in the switch flash memory., stored in the switch flash memory.

Recover from system crashRecover from system crash

• The boot loader also provides access into the The boot loader also provides access into the switch if the operating system cannot be used. switch if the operating system cannot be used.

• The boot loader has a command-line facility that The boot loader has a command-line facility that provides access to the files stored on Flash provides access to the files stored on Flash memory before the operating system is loaded. memory before the operating system is loaded.

• From the boot loader command line you can From the boot loader command line you can enter commands enter commands to format the flash file system, to format the flash file system, reinstall the operating system software image, or reinstall the operating system software image, or recover from a lost or forgotten passwordrecover from a lost or forgotten password..

Managing interfaces (1)Managing interfaces (1)• An access layer switch is much like a PC in that you An access layer switch is much like a PC in that you

need to configure an IP address, a subnet mask, and a need to configure an IP address, a subnet mask, and a default gatewaydefault gateway. .

• To manage a switch remotely using TCP/IP, you need To manage a switch remotely using TCP/IP, you need to assign the switch an IP address. to assign the switch an IP address.

• In the figure, you want to manage S1 from PC1, a In the figure, you want to manage S1 from PC1, a computer used for managing the network. To do this, computer used for managing the network. To do this, you need to assign switch S1 an IP address. you need to assign switch S1 an IP address. – This IP address is assigned to a virtual interface called a This IP address is assigned to a virtual interface called a

virtual LAN (VLAN), and then it is necessary to ensure the virtual LAN (VLAN), and then it is necessary to ensure the VLAN is assigned to a specific port or ports on the switch. VLAN is assigned to a specific port or ports on the switch.

• The default configuration on the switch is to have the The default configuration on the switch is to have the management of the switch controlled through VLAN 1. management of the switch controlled through VLAN 1. However, a best practice for basic switch However, a best practice for basic switch configuration is to change the management VLAN to a configuration is to change the management VLAN to a VLAN other than VLAN 1. VLAN other than VLAN 1.

Managing interfaces (2)Managing interfaces (2)




• Use the Use the show ip interface briefshow ip interface brief to verify port operation and to verify port operation and status.status.

• The The mdix automdix auto Command Command

• When the auto-MDIX feature is enabled, the switch detects When the auto-MDIX feature is enabled, the switch detects the required cable type for copper Ethernet connections and the required cable type for copper Ethernet connections and configures the interfaces accordingly. configures the interfaces accordingly. – Therefore, you can use either a crossover or a straight-through Therefore, you can use either a crossover or a straight-through

cable for connections to a copper 10/100/1000 port on the cable for connections to a copper 10/100/1000 port on the switch, regardless of the type of device on the other end of the switch, regardless of the type of device on the other end of the connection.connection.

• The auto-MDIX feature is enabled by default on switches The auto-MDIX feature is enabled by default on switches running Cisco IOS Release 12.2(18)SE or later. For releases running Cisco IOS Release 12.2(18)SE or later. For releases between Cisco IOS Release 12.1(14)EA1 and 12.2(18)SE, the between Cisco IOS Release 12.1(14)EA1 and 12.2(18)SE, the auto-MDIX feature is disabled by default.auto-MDIX feature is disabled by default.


• Configure Duplex and SpeedConfigure Duplex and Speed• You can use theYou can use the duplex duplex interface interface

configuration command to specify the configuration command to specify the duplex mode of operation for switch ports. duplex mode of operation for switch ports.

• You can manually set the duplex mode and You can manually set the duplex mode and speed of switch ports speed of switch ports to avoid inter-vendor to avoid inter-vendor issues with autonegotiation.issues with autonegotiation.

• Although there can be issues when you Although there can be issues when you configure switch port duplex settings to configure switch port duplex settings to auto, in this example, S1 and S2 switches auto, in this example, S1 and S2 switches have the same duplex settings and speeds. have the same duplex settings and speeds.


Managing MAC Address Managing MAC Address Table(1)Table(1)• Switches use MAC address tables to determine Switches use MAC address tables to determine

how to forward traffic between ports. how to forward traffic between ports. – These MAC tables include dynamic and static addresses. These MAC tables include dynamic and static addresses.

• Dynamic addressesDynamic addresses are source MAC addresses are source MAC addresses that the switch learns and then ages when they that the switch learns and then ages when they are not in use. are not in use.

• You can change the aging time setting for MAC You can change the aging time setting for MAC addresses. addresses. – The default time is 300 secondsThe default time is 300 seconds. . – Setting too short an aging time can cause addresses to Setting too short an aging time can cause addresses to

be prematurely removed from the table. be prematurely removed from the table. – Setting too long an aging time can cause the address Setting too long an aging time can cause the address

table to be filled with unused addresses, which prevents table to be filled with unused addresses, which prevents new addresses from being learned. new addresses from being learned.

Managing MAC Address Managing MAC Address Table(2)Table(2)• The switch provides dynamic addressing by The switch provides dynamic addressing by

learning the source MAC address of each learning the source MAC address of each frame that it receives on each port.frame that it receives on each port.

• Then switch adds the source MAC address Then switch adds the source MAC address and its associated port number to the MAC and its associated port number to the MAC address table. address table.

• As computers are added or removed from As computers are added or removed from the network, the switch updates the MAC the network, the switch updates the MAC address table, adding new entries and aging address table, adding new entries and aging out those that are currently not in use.out those that are currently not in use.

Managing MAC Address Managing MAC Address Table(3)Table(3)• A network administrator can specifically assign A network administrator can specifically assign

static MAC addresses to certain ports. static MAC addresses to certain ports. • Static addressesStatic addresses are not aged out, and the are not aged out, and the

switch always knows which port to send out switch always knows which port to send out traffic destined for that specific MAC address.traffic destined for that specific MAC address.

• As a result, there is no need to relearn or As a result, there is no need to relearn or refresh which port the MAC address is refresh which port the MAC address is connected to. connected to.

• One reason to implement static MAC addresses One reason to implement static MAC addresses is to provide the network administrator is to provide the network administrator complete control over access to the networkcomplete control over access to the network..– Only those devices that are known to the network Only those devices that are known to the network

administrator can connect to the network.administrator can connect to the network.

Managing MAC Address Managing MAC Address Table(4)Table(4)• To create a static mapping in the MAC address To create a static mapping in the MAC address

table, use the table, use the – mac-address-table static <MAC address> vlan {1-4096, mac-address-table static <MAC address> vlan {1-4096,

ALL} interfaceinterface-idALL} interfaceinterface-id

• To remove a static mapping in the MAC address To remove a static mapping in the MAC address table, use the table, use the – no mac-address-table static <MAC address> vlan {1-no mac-address-table static <MAC address> vlan {1-

4096, ALL} interfaceinterface-id4096, ALL} interfaceinterface-id

• The maximum size of the MAC address table The maximum size of the MAC address table varies with different switches. varies with different switches. – For example, the Catalyst 2960 series switch can store up For example, the Catalyst 2960 series switch can store up

to 8,192 MAC addresses. to 8,192 MAC addresses. – There are other protocols that may limit the absolute There are other protocols that may limit the absolute

number of MAC address available to a switch.number of MAC address available to a switch.

Verifying switch Verifying switch configurationconfiguration

Backup and Restore switch Backup and Restore switch configurationsconfigurations

Backup to TFTP serverBackup to TFTP server

• Step 1. Verify that the TFTP server is running on your Step 1. Verify that the TFTP server is running on your network.network.

• Step 2. Log in to the switch through the console port or a Step 2. Log in to the switch through the console port or a Telnet session. Enable the switch and then ping the TFTP Telnet session. Enable the switch and then ping the TFTP server.server.

• Step 3. Upload the switch configuration to the TFTP server. Step 3. Upload the switch configuration to the TFTP server. Specify the IP address or hostname of the TFTP server and Specify the IP address or hostname of the TFTP server and the destination filename. The Cisco IOS command is: the destination filename. The Cisco IOS command is:

#copy system:running-config #copy system:running-config tftp:[[[//location]/directory]/filename] tftp:[[[//location]/directory]/filename] #copy nvram:startup-config #copy nvram:startup-config tftp:[[[//location]/directory]/filename].tftp:[[[//location]/directory]/filename].

Restore from TFTP serverRestore from TFTP server

• Step 1. Copy the configuration file to the appropriate TFTP Step 1. Copy the configuration file to the appropriate TFTP directory on the TFTP server if it is not already there.directory on the TFTP server if it is not already there.

• Step 2. Verify that the TFTP server is running on your Step 2. Verify that the TFTP server is running on your network.network.

• Step 3. Log in to the switch through the console port or a Step 3. Log in to the switch through the console port or a Telnet session. Enable the switch and then ping the TFTP Telnet session. Enable the switch and then ping the TFTP server.server.

• Step 4. Download the configuration file from the TFTP server Step 4. Download the configuration file from the TFTP server to configure the switch. Specify the IP address or hostname of to configure the switch. Specify the IP address or hostname of the TFTP server and the name of the file to download. The the TFTP server and the name of the file to download. The Cisco IOS command is: Cisco IOS command is: #copy tftp:[[[//location]/directory]/filename] system:running-#copy tftp:[[[//location]/directory]/filename] system:running-config or #copy tftp:[[[//location]/directory]/filename] config or #copy tftp:[[[//location]/directory]/filename] nvram:startup-config.nvram:startup-config.

Clearing Configuration Clearing Configuration Information Information • You can clear the configuration information from You can clear the configuration information from

the startup configuration. the startup configuration. • To clear the contents of your startup configuration, To clear the contents of your startup configuration,

use the use the – erase nvram: erase nvram: – erase startup-configerase startup-config

Configure Console PasswordConfigure Console Password

Configure Virtual Terminal Configure Virtual Terminal AccessAccess

Configure EXEC Mode Configure EXEC Mode PasswordPassword

Password Recovery steps Password Recovery steps (1)(1)• Step 1. Connect a terminal or PC with Step 1. Connect a terminal or PC with

terminal-emulation software to the switch terminal-emulation software to the switch console port.console port.

• Step 2. Set the line speed on the emulation Step 2. Set the line speed on the emulation software to 9600 baud.software to 9600 baud.

• Step 3. Power off the switch. Reconnect the Step 3. Power off the switch. Reconnect the power cord to the switch and within 15 power cord to the switch and within 15 seconds, press the Mode button while the seconds, press the Mode button while the System LED is still flashing green. Continue System LED is still flashing green. Continue pressing the Mode button until the System pressing the Mode button until the System LED turns briefly amber and then solid LED turns briefly amber and then solid green. Then release the Mode button.green. Then release the Mode button.

Password Recovery steps Password Recovery steps (2)(2)

• Step 4. Initialize the Flash file system Step 4. Initialize the Flash file system using the flash_init command.using the flash_init command.

• Step 5. Load any helper files using the Step 5. Load any helper files using the load_helper command.load_helper command.

• Step 6. Display the contents of Flash Step 6. Display the contents of Flash memory using the dir flash command:memory using the dir flash command:

Directory of flash:Directory of flash:13 drwx 192 Mar 01 1993 22:30:48 c2960-lanbase-mz.122-25.FX13 drwx 192 Mar 01 1993 22:30:48 c2960-lanbase-mz.122-25.FX11 -rwx 5825 Mar 01 1993 22:31:59 config.text11 -rwx 5825 Mar 01 1993 22:31:59 config.text18 -rwx 720 Mar 01 1993 02:21:30 vlan.dat18 -rwx 720 Mar 01 1993 02:21:30 vlan.dat16128000 bytes total (10003456 bytes free)16128000 bytes total (10003456 bytes free)

Password Recovery steps Password Recovery steps (3)(3)• Step 7. Rename the configuration file to Step 7. Rename the configuration file to

config.text.old, which contains the password config.text.old, which contains the password definition, using the definition, using the rename flash:config.text rename flash:config.text flash:config.text.oldflash:config.text.old command. command.

• Step 8. Boot the system with the Step 8. Boot the system with the bootboot command. command. • Step 9. You are prompted to start the setup Step 9. You are prompted to start the setup

program. program. – Enter N at the prompt, and then when the system prompts Enter N at the prompt, and then when the system prompts

whether to continue with the configuration dialog, enter N.whether to continue with the configuration dialog, enter N.

• Step 10. At the switch prompt, enter privileged Step 10. At the switch prompt, enter privileged EXEC mode using the enable command.EXEC mode using the enable command.

• Step 11. Rename the configuration file to its original Step 11. Rename the configuration file to its original name using the name using the rename flash:config.text.old rename flash:config.text.old flash:config.textflash:config.text command. command.

Password Recovery steps Password Recovery steps (4)(4)• Step 12. Copy the configuration file into memory Step 12. Copy the configuration file into memory

using the using the copy flash:config.text system:running-copy flash:config.text system:running-configconfig command. After this command has been command. After this command has been entered, the follow is displayed on the console:entered, the follow is displayed on the console:

Source filename [config.text]? Source filename [config.text]? Destination filename [running-config]?Destination filename [running-config]?

• Press Return in response to the confirmation Press Return in response to the confirmation prompts. The configuration file is now reloaded, prompts. The configuration file is now reloaded, and you can change the password.and you can change the password.

• Step 13. Enter global configuration mode using the Step 13. Enter global configuration mode using the configure terminalconfigure terminal command. command.

Password Recovery steps Password Recovery steps (5)(5)• Step 14. Change the password using the Step 14. Change the password using the enable enable

secretpasswordsecretpassword command. command.

• Step 15. Return to privileged EXEC mode using the Step 15. Return to privileged EXEC mode using the exitexit command. command.

• Step 16. Write the running configuration to the Step 16. Write the running configuration to the startup configuration file using the startup configuration file using the copy running-copy running-config startup-configconfig startup-config command. command.

• Step 17. Reload the switch using the Step 17. Reload the switch using the reloadreload command.command.

Configure Login & MOTD Configure Login & MOTD BannerBanner

Configuring Telnet Configuring Telnet

• Telnet is the default vty-supported protocol Telnet is the default vty-supported protocol on a Cisco switch. on a Cisco switch.

• Initially, the vty lines are unsecured Initially, the vty lines are unsecured allowing access by any user attempting to allowing access by any user attempting to connect to themconnect to them

Configuring Port security (1)Configuring Port security (1)

• Secure MAC Address TypesSecure MAC Address Types

• Static secure MAC addressesStatic secure MAC addresses: MAC addresses are manually : MAC addresses are manually configured by using the configured by using the switchport port-security mac-switchport port-security mac-addressmac-addressaddressmac-address interface configuration command. interface configuration command. – MAC addresses configured in this way are stored in the address MAC addresses configured in this way are stored in the address

table and are added to the running configuration on the switch. table and are added to the running configuration on the switch.

• Dynamic secure MAC addressesDynamic secure MAC addresses: MAC addresses are : MAC addresses are dynamically learned and stored only in the address table. dynamically learned and stored only in the address table. – MAC addresses configured in this way are removed when the MAC addresses configured in this way are removed when the

switch restarts. switch restarts.

• Sticky secure MAC addressesSticky secure MAC addresses: You can configure a port to : You can configure a port to dynamically learn MAC addresses and then save these MAC dynamically learn MAC addresses and then save these MAC addresses to the running configuration. addresses to the running configuration.


• Sticky MAC AddressesSticky MAC Addresses

• When you enable sticky learning on an When you enable sticky learning on an interface by using the interface by using the switchport port-switchport port-security mac-address stickysecurity mac-address sticky interface interface configuration command,configuration command,– the interface converts all the dynamic secure the interface converts all the dynamic secure

MAC addresses, including those that were MAC addresses, including those that were dynamically learned before sticky learning was dynamically learned before sticky learning was enabled, to sticky secure MAC addresses and adds enabled, to sticky secure MAC addresses and adds all sticky secure MAC addresses to the running all sticky secure MAC addresses to the running configuration. configuration.


• When you configure sticky secure MAC When you configure sticky secure MAC addresses by using the addresses by using the switchport switchport port-security mac-address sticky mac-port-security mac-address sticky mac-addressaddress interface configuration interface configuration command, these addresses are added command, these addresses are added to the address table and the running to the address table and the running configuration.configuration.– If port security is disabled, the sticky If port security is disabled, the sticky

secure MAC addresses remain in the secure MAC addresses remain in the running configuration. running configuration.


• Security Violation ModesSecurity Violation Modes

• Violation modes are configured on a port: Violation modes are configured on a port: – protectprotect: When the number of secure MAC : When the number of secure MAC

addresses reaches the limit allowed on the addresses reaches the limit allowed on the port, packets with unknown source port, packets with unknown source addresses are addresses are droppeddropped until you remove a until you remove a sufficient number of secure MAC addresses sufficient number of secure MAC addresses or increase the number of maximum or increase the number of maximum allowable addresses. allowable addresses. •You are not notified that a security violation has You are not notified that a security violation has

occurredoccurred. .


• restrictrestrict: When the number of secure MAC addresses : When the number of secure MAC addresses reaches the limit allowed on the port, packets with reaches the limit allowed on the port, packets with unknown source addresses are unknown source addresses are droppeddropped until you until you remove a sufficient number of secure MAC addresses remove a sufficient number of secure MAC addresses or increase the number of maximum allowable or increase the number of maximum allowable addresses. addresses. – In this mode, In this mode, you are notified that a security violation has you are notified that a security violation has

occurred. Specifically, an SNMP trap is sent, a syslog message occurred. Specifically, an SNMP trap is sent, a syslog message is logged, and the violation counter increments. is logged, and the violation counter increments.

• shutdownshutdown: In this mode, a port security violation : In this mode, a port security violation causes the interface to immediately become causes the interface to immediately become error-error-disabled and turns off the port LEDdisabled and turns off the port LED. . – It also sends an SNMP trap, logs a syslog message, and It also sends an SNMP trap, logs a syslog message, and

increments the violation counter. increments the violation counter. – When a secure port is in the error-disabled state, you can bring When a secure port is in the error-disabled state, you can bring

it out of this state by entering the shutdown and no shutdown it out of this state by entering the shutdown and no shutdown interface configuration commands. This is the default mode.interface configuration commands. This is the default mode.





Configuring Port security Configuring Port security (10)(10)

Configuring Port security Configuring Port security (11)(11)

Configuring Port security Configuring Port security (12)(12)• Disable Unused PortsDisable Unused Ports

• A simple method many administrators use to help A simple method many administrators use to help secure their network from unauthorized access is secure their network from unauthorized access is to disable all unused ports on a network switch. to disable all unused ports on a network switch.

• It is simple to disable multiple ports on a switch. It is simple to disable multiple ports on a switch. Navigate to each unused port and issue this Cisco Navigate to each unused port and issue this Cisco IOS IOS shutdownshutdown command. command.

• An alternate way to shutdown multiple ports is to An alternate way to shutdown multiple ports is to use the use the interface rangeinterface range command. command. – If a port needs to be activated, you can manually enter If a port needs to be activated, you can manually enter

the no shutdown command on that interface.the no shutdown command on that interface.

Documents

Basic Switch configuration