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ITE PC v4.0 Chapter 1

Chapter 5: Switch Configuration
Routing and Switching Essentials v6.0

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Cisco Networking Academy Program
Routing and Switching Essentials v6.0
Chapter 5: Switch Configuration

Chapter 5 – Sections & Objectives
5.1 Basic Switch Configuration
Configure initial settings on a Cisco switch.
Configure switch ports to meet network requirements.
5.2 Switch Security: Management and Implementation
Configure the management virtual interface on a switch.
Configure the port security feature to restrict network access.

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5.1 Basic Switch Configuration

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Cisco Networking Academy Program
Routing and Switching Essentials v6.0
Chapter 5: Switch Configuration

Configure a Switch with Initial Settings
Switch Boot Sequence
Power-on self test (POST).
Run boot loader software.
Boot loader performs low-level CPU initialization.
Boot loader initializes the flash file system.
Boot loader locates and loads a default IOS operating system software image into memory and passes control of the switch over to the IOS.

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5.1 – Basic Switch Configuration
5.1.1 – Configure a Switch with Initial Settings
5.1.1.1 Switch Boot Sequence

Configure a Switch with Initial Settings
Switch Boot Sequence (cont.)
To find a suitable Cisco IOS image, the switch goes through the following steps:
Step 1. It attempts to automatically boot by using information in the BOOT environment variable.
Step 2. If this variable is not set, the switch performs a top-to-bottom search through the flash file system. It loads and executes the first executable file, if it can.
Step 3. The IOS software then initializes the interfaces using the Cisco IOS commands found in the configuration file and startup configuration, which is stored in NVRAM.
Note: The boot system command can be used to set the BOOT environment variable. Use the show boot command to see to what the current IOS boot file is set.

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5.1 – Basic Switch Configuration
5.1.1 – Configure a Switch with Initial Settings
5.1.1.1 Switch Boot Sequence (cont.)

Configure a Switch with Initial Settings
Recovering From a System Crash
The boot loader can also be used to manage the switch if the IOS cannot be loaded.
The boot loader can be accessed through a console connection by:
Connecting a PC by console cable to the switch console port. Unplug the switch power cord.
Reconnecting the power cord to the switch and press and hold the Mode button.
The System LED turns briefly amber and then solid green. Release the Mode button.
The boot loader switch: prompt appears in the terminal emulation software on the PC.

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5.1 – Basic Switch Configuration
5.1.1 – Configure a Switch with Initial Settings
5.1.1.2 – Recovering From a System Crash

Configure a Switch with Initial Settings
Switch LED Indicators
Each port on Cisco Catalyst switches have status LED indicator lights.
By default, these LED lights reflect port activity, but they can also provide other information about the switch through the Mode button.
The following modes are available on Cisco Catalyst 2960 switches:
System LED
Redundant Power System (RPS) LED
Port Status LED
Port Duplex LED
Port Speed LED
Power over Ethernet (PoE) Mode LED

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5.1 – Basic Switch Configuration
5.1.1 – Configure a Switch with Initial Settings
5.1.1.3 – Switch LED Indicators

Configure a Switch with Initial Settings
Preparing for Basic Switch Management
To remotely manage a Cisco switch, it must be configured to access the network.
A console cable is used to connect a PC to the console port of a switch for configuration.
The IP information (address, subnet mask, gateway) is to be assigned to a switch virtual interface (SVI).
If managing the switch from a remote network, a default gateway must also be configured.
Although these IP settings allow remote management and remote access to the switch, they do not allow the switch to route Layer 3 packets.

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5.1 – Basic Switch Configuration
5.1.1 – Configure a Switch with Initial Settings
5.1.1.4 – Preparing for Basic Switch Management

Configure a Switch with Initial Settings
Configuring Switch Management Access

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5.1 – Basic Switch Configuration
5.1.1 – Configure a Switch with Initial Settings
5.1.1.5 – Configuring Basic Switch Management Access with IPv4

Configure a Switch with Initial Settings
Configuring Switch Management Access (cont.)

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5.1 – Basic Switch Configuration
5.1.1 – Configure a Switch with Initial Settings
5.1.1.5 – Configuring Basic Switch Management Access with IPv4 (cont.)

Configure a Switch with Initial Settings
Configuring Switch Management Access (cont.)

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5.1 – Basic Switch Configuration
5.1.1 – Configure a Switch with Initial Settings
5.1.1.5 – Configuring Basic Switch Management Access with IPv4 (cont.)

Configure Switch Ports
Duplex Communication

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5.1 – Basic Switch Configuration
5.1.2 – Configure Switch Ports
5.1.2.1 – Duplex Communication

Configure Switch Ports
Configure Switch Ports at the Physical Layer

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5.1 – Basic Switch Configuration
5.1.2 – Configure Switch Ports
5.1.2.2 – Configure Switch Ports at the Physical Layer

Configure Switch Ports
Auto-MDIX
Certain cable types (straight-through or crossover) were historically required when connecting devices.
The automatic medium-dependent interface crossover (auto-MDIX) feature eliminates this problem.
When auto-MDIX is enabled, the interface automatically detects and appropriately configures the connection.
When using auto-MDIX on an interface, the interface speed and duplex must be set to auto.

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5.1 – Basic Switch Configuration
5.1.2 – Configure Switch Ports
5.1.2.3 – Auto-MDIX

Configure Switch Ports
Auto-MDIX (cont.)

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5.1 – Basic Switch Configuration
5.1.2 – Configure Switch Ports
5.1.2.3 – Auto-MDIX

Configure Switch Ports
Auto-MDIX (cont.)

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5.1 – Basic Switch Configuration
5.1.2 – Configure Switch Ports
5.1.2.3 – Auto-MDIX

Configure Switch Ports
Verifying Switch Port Configuration

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5.1 – Basic Switch Configuration
5.1.2 – Configure Switch Ports
5.1.2.4 – Verifying Switch Port Configuration

Configure Switch Ports
Network Access Layer Issue

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5.1 – Basic Switch Configuration
5.1.2 – Configure Switch Ports
5.1.2.5 – Network Access Layer Issue

Configure Switch Ports
Network Access Layer Issue (cont.)

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5.1 – Basic Switch Configuration
5.1.2 – Configure Switch Ports
5.1.2.5 – Network Access Layer Issue

Configure Switch Ports
Troubleshooting Network Access Layer Issues

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5.1 – Basic Switch Configuration
5.1.2 – Configure Switch Ports
5.1.2.6 – Troubleshooting Network Access Layer Issues

5.2 Switch Security: Management and Implementation

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Cisco Networking Academy Program
Routing and Switching Essentials v6.0
Chapter 5: Switch Configuration

Secure Remote Access
SSH Operation
Secure Shell (SSH) is a protocol that provides a secure (encrypted), command-line based connection to a remote device.
Because of strong encryption features, SSH should replace Telnet for management connections.
SSH uses TCP port 22, by default.
Telnet uses TCP port 23.
A version of the IOS software, including cryptographic (encrypted) features and capabilities, is required to enable SSH on Catalyst 2960 switches.

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5.2 – Switch Security: Management and Implementation
5.2.1 – Secure Remote Access
5.2.1.1 – SSH Operation

Secure Remote Access
Configuring SSH

Verify SHH Support – show ip ssh

Configure the IP domain.

Generate RSA key pairs.

Configure user authentication.

Configure the vty lines.

Enable SSH version 2.

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5.2 – Switch Security: Management and Implementation
5.2.1 – Secure Remote Access
5.2.1.2 – Configuring SSH

Secure Remote Access
Verifying SSH

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5.2 – Switch Security: Management and Implementation
5.2.1 – Secure Remote Access
5.2.1.3 – Verifying SSH

Secure Remote Access
Verifying SSH (cont.)

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5.2 – Switch Security: Management and Implementation
5.2.1 – Secure Remote Access
5.2.1.3 – Verifying SSH

Switch Port Security
Secure Unused Ports

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5.2 – Switch Security: Management and Implementation
5.2.1 – Switch Port Security
5.2.2.1 – Secure Unused Ports

Switch Port Security
Port Security: Operation
The MAC addresses of legitimate devices are allowed access, while other MAC addresses are denied.
Any additional attempts to connect by unknown MAC addresses generate a security violation.
Secure MAC addresses can be configured in a number of ways:
Static secure MAC addresses – manually configured and added to running configuration – switchport port-security mac-address mac-address
Dynamic secure MAC addresses – removed when switch restarts
Sticky secure MAC addresses – added to running configuration and learned dynamically – switchport port-security mac-address sticky interface configuration mode command

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5.2 – Switch Security: Management and Implementation
5.2.2 – Switch Port Security
5.2.2.2 – Port Security: Operation

Switch Port Security
Port Security: Violation Modes
IOS considers a security violation when:
The maximum number of secure MAC addresses for that interface have been added to the CAM, and a station whose MAC address is not in the address table attempts to access the interface.
There are three possible actions to take when a violation is detected:
Protect – no notification received
Restrict – notification received of security violation
Shutdown
switchport port-security violation {protect | restrict |shutdown} interface configuration mode command

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5.2 – Switch Security: Management and Implementation
5.2.2 – Switch Port Security
5.2.2.3 – Port Security: Violation Modes

Switch Port Security
Port Security: Violation Modes (cont.)

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5.2 – Switch Security: Management and Implementation
5.2.2 – Switch Port Security
5.2.2.3 – Port Security: Violation Modes

Switch Port Security
Port Security: Configuring

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5.2 – Switch Security: Management and Implementation
5.2.2 – Switch Port Security
5.2.2.4 – Port Security: Configuring

Switch Port Security
Port Security: Verifying

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5.2 – Switch Security: Management and Implementation
5.2.2 – Switch Port Security
5.2.2.5 – Port Security: Verifying

Switch Port Security
Port Security: Verifying (cont.)

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5.2 – Switch Security: Management and Implementation
5.2.2 – Switch Port Security
5.2.2.5 – Port Security: Verifying

Switch Port Security
Ports in Error Disabled State
A port security violation can put a switch in error disabled state.
A port in error disabled is effectively shutdown.
The switch communicates these events through console messages.

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5.2 – Switch Security: Management and Implementation
5.2.2 – Switch Port Security
5.2.2.6 – Ports in Error Disabled State

Switch Port Security
Ports in Error Disabled State (cont.)

The show interface command also reveals a switch port on error disabled state.

A shutdown or no shutdown interface configuration mode command must be issued to re-enable the port.

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5.2 – Switch Security: Management and Implementation
5.2.2 – Switch Port Security
5.2.2.6 – Ports in Error Disabled State

5.3 Chapter Summary

Cisco LAN switch boot sequence.
Cisco LAN switch LED modes.
How to remotely access and manage a Cisco LAN switch through a secure connection.
Cisco LAN switch port duplex modes.
Cisco LAN switch port security, violation modes, and actions.
Best practices for switched networks.

Chapter Summary
Summary

When a Cisco LAN switch is first powered on it goes through the following boot sequence:
1. First, the switch loads a power-on self-test (POST) program stored in ROM. POST checks the CPU subsystem. It tests the CPU, DRAM, and the portion of the flash device that makes up the flash file system.
2. Next, the switch loads the boot loader software. The boot loader is a small program stored in ROM and is run immediately after POST successfully completes.
3. The boot loader performs low-level CPU initialization. It initializes the CPU registers, which control where physical memory is mapped, the quantity of memory, and its speed.
4. The boot loader initializes the flash file system on the system board.
5. Finally, the boot loader locates and loads a default IOS operating system software image into memory and gives control of the switch over to the IOS.
If the Cisco IOS files are missing or damaged, the boot loader program can be used to reload or recover from the problem.
The operational status of the switch is displayed by a series of LEDs on the front panel. These LEDs display such things as port status, duplex, and speed.
Chapter Summary
Summary

An IP address is configured on the SVI of the management VLAN to allow for remote configuration of the device. A default gateway belonging to the management VLAN must be configured on the switch using the ip default-gateway command. If the default gateway is not properly configured, remote management is not possible.
It is recommended that Secure Shell (SSH) be used to provide a secure (encrypted) management connection to a remote device to prevent the sniffing of unencrypted user names and passwords, which is possible when using protocols such as Telnet.
One of the advantages of a switch is that it allows full-duplex communication between devices, effectively doubling the communication rate. Although it is possible to specify the speed and duplex settings of a switch interface, it is recommended that the switch be allowed to set these parameters automatically to avoid errors.
Port security is only one defense against network compromise.
Chapter Summary
Summary

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