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Chapter 5 Switch Configuration (Basic Switch Configuration (Configure a…

- - - - After a Cisco switch is powered on, it goes through the following boot sequence:
        
        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.
        
        Next, the switch loads the boot loader software.
        
        The boot loader is a small program stored in ROM that is run immediately after POST successfully completes.
        
        Performs low-level CPU initialization. It initializes the CPU registers, which control where physical memory is mapped, the quantity of memory, and its speed.
        
        The boot loader initializes the flash file system on the system board.
        
        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.
        
        The boot loader finds the Cisco IOS image on the switch as follows:
        
        The switch attempts to automatically boot by using information in the BOOT environment variable.
        
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    - - The boot loader provides access into the switch if the operating system cannot be used because of missing or damaged system files
        
        Because of missing or damaged system files. The boot loader has a command-line that provides access to the files stored in flash memory.
        
        The boot loader can be accessed through a console connection following these steps:
        
        Step 1. Connect a PC by console cable to the switch console port. Configure terminal emulation software to connect to the switch.
        
        Step 2. Unplug the switch power cord.
        
        Step 3. Reconnect the power cord to the switch and, within 15 seconds, press and hold down the Mode button while the System LED is still flashing green.
        
        Step 4. Continue pressing the Mode button until the System LED turns briefly amber and then solid green; then release the Mode button.
        
        Step 5. The boot loader switch: prompt appears in the terminal emulation software on the PC.
        
        The boot loader command line supports commands to format the flash file system, reinstall the operating system software, and recover a lost or forgotten password
        
        For example, the dir command can be used to view a list of files within a specified directory, as shown in the figure (dir flash:)
    - - System LED - Shows whether the system is receiving power and is functioning properly. If the LED is off, it means the system is not powered on. If the LED is green, the system is operating normally. If the LED is amber, the system is receiving power but is not functioning properly.
      - Redundant Power System (RPS) LED - Shows the RPS status. If the LED is off, the RPS is off, or it is not properly connected. If the LED is green, the RPS is connected and ready to provide backup power. If the LED is blinking green, the RPS is connected but is unavailable because it is providing power to another device. If the LED is amber, the RPS is in standby mode, or in a fault condition. If the LED is blinking amber, the internal power supply in the switch has failed, and the RPS is providing power.
      - Port Status LED - Indicates that the port status mode is selected when the LED is green. This is the default mode. When selected, the port LEDs will display colors with different meanings. If the LED is off, there is no link, or the port was administratively shut down. If the LED is green, a link is present. If the LED is blinking green, there is activity and the port is sending or receiving data. If the LED is alternating green-amber, there is a link fault. If the LED is amber, the port is blocked to ensure that a loop does not exist in the forwarding domain and is not forwarding data (typically, ports will remain in this state for the first 30 seconds after being activated). If the LED is blinking amber, the port is blocked to prevent a possible loop in the forwarding domain.
      - Port Duplex LED - Indicates the port duplex mode is selected when the LED is green. When selected, port LEDs that are off are in half-duplex mode. If the port LED is green, the port is in full-duplex mode.
      - Port Speed LED - Indicates the port speed mode is selected. When selected, the port LEDs will display colors with different meanings. If the LED is off, the port is operating at 10 Mb/s. If the LED is green, the port is operating at 100 Mb/s. If the LED is blinking green, the port is operating at 1000 Mb/s.
      - Power over Ethernet (PoE) Mode LED - If PoE is supported; a PoE mode LED will be present. If the LED is off, it indicates the PoE mode is not selected and that none of the ports have been denied power or placed in a fault condition. If the LED is blinking amber, the PoE mode is not selected but at least one of the ports has been denied power, or has a PoE fault. If the LED is green, it indicates the PoE mode is selected and the port LEDs will display colors with different meanings. If the port LED is off, the PoE is off. If the port LED is green, the PoE is on. If the port LED is alternating green-amber, PoE is denied because providing power to the powered device will exceed the switch power capacity. If the LED is blinking amber, PoE is off due to a fault. If the LED is amber, PoE for the port has been disabled.
  - - - When a switch port is operating in full-duplex mode, there is no collision domain associated with the port.
    - - Use the duplex interface configuration mode command to manually specify the duplex mode for a switch port.
      - Use the speed interface configuration mode command to manually specify the speed for a switch port.
      - When troubleshooting switch port issues, the duplex and speed settings should be checked.
        
        Auto-negotiation is useful when the speed and duplex settings of the device connecting to the port are unknown or may change.
  - - - the mdix auto interface configuration mode command enables the feature.
        
        When using auto-MDIX on an interface, the interface speed and duplex must be set to auto so that the feature operates correctly.
        
        To examine the auto-MDIX setting for a specific interface, use the show controllers ethernet-controller interface_type interface_id phy | include Auto-MDIX
- - - - Navigate to each unused port and issue the Cisco IOS shutdown command
        
        It is simple to make configuration changes to multiple ports on a switch. If a range of ports must be configured, use the interface range command.
        
        Switch(config)# interface range type module/first-number – last-number
    - - The port security feature will not work until port security is enabled on the interface using the "switchport port-security" command.
        
        One way to secure ports is by implementing a feature called port security.
        
        Port security limits the number of valid MAC addresses allowed on a port
        
        If a port is configured as a secure port and the maximum number of MAC addresses is reached, any additional attempts to connect by unknown MAC addresses will generate a security violation.
        
        Port Security: Violation Modes
        
        To change the violation mode on a switch port, use the switchport port-security violation {protect | restrict | shutdown} interface configuration mode command.
        
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        use switchport port-security maximum # to set he maximum number of secure addresses allowed on the port
        
        Secure MAC Address Types
        
        Static secure MAC addresses - MAC addresses that are manually configured on a port by using the switchport port-security mac-address mac-address interface configuration mode command.
        
        MAC addresses configured in this way are stored in the address table and are added to the running configuration on the switch.
        
        Dynamic secure MAC addresses - MAC addresses that are dynamically learned and stored only in the address table.
        
        MAC addresses configured in this way are removed when the switch restarts.
        
        Sticky secure MAC addresses - MAC addresses that can be dynamically learned or manually configured, then stored in the address table and added to the running configuration.
        
        Sticky learning is enabled on an interface by using the switchport port-security mac-address sticky interface configuration mode command.
        
        When this command is entered, the switch converts all dynamically learned MAC addresses, including those that were dynamically learned before sticky learning was enabled, into sticky secure MAC addresses. All sticky secure MAC addresses are added to the address table and to the running configuration.
        
        Sticky secure MAC addresses can also be manually defined. When sticky secure MAC addresses are configured by using the switchport port-security mac-address sticky mac-address interface configuration mode command, all specified addresses are added to the address table and the running configuration.
      - Verify Port Security Settings
        
        To display port security settings for the switch, or for the specified interface, use the show port-security interface [interface-id] command
        
        show run shows the values for the sticky port security settings.
        
        To display all secure MAC addresses configured on all switch interfaces, or on a specified interface with aging information for each, use the show port-security address command.