Configure a Switch with Initial Settings

1.1.1

Switch Boot Sequence

Before you can configure a switch, you need to turn it on and allow it to go through the five-step boot sequence. This topic covers the basics of configuring a switch and includes a lab at the end.

After a Cisco switch is powered on, it goes through the following five-step boot sequence:

Step 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.
Step 2: 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.
Step 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.
Step 4: The boot loader initializes the flash file system on the system board.
Step 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.

1.1.2

The boot system Command

The switch attempts to automatically boot by using information in the BOOT environment variable. If this variable is not set, the switch attempts to load and execute the first executable file it can find. On Catalyst 2960 Series switches, the image file is normally contained in a directory that has the same name as the image file (excluding the .bin file extension).

The IOS operating system then initializes the interfaces using the Cisco IOS commands found in the startup-config file. The startup-config file is called config.text and is located in flash.

In the example, the BOOT environment variable is set using the boot system global configuration mode command. Notice that the IOS is located in a distinct folder and the folder path is specified. Use the command show boot to see what the current IOS boot file is set to.

S1(config)# boot system flash:/c2960-lanbasek9-mz.150-2.SE/c2960-lanbasek9-mz.150-2.SE.bin

The table defines each part of the boot system command.

Table caption
Command Definition
boot system
The main command
flash: 
The storage device
c2960-lanbasek9-mz.150-2.SE/
The path to the file system
c2960-lanbasek9-mz.150-2.SE.bin
The IOS file name
1.1.3

Switch LED Indicators

Cisco Catalyst switches have several status LED indicator lights. You can use the switch LEDs to quickly monitor switch activity and performance. Switches of different models and feature sets will have different LEDs and their placement on the front panel of the switch may also vary.

The figure shows the switch LEDs and the Mode button for a Cisco Catalyst 2960 switch.

The figure shows LED indicators, the mode button, and ports on the front left side of a switch. The LED indicators numbered 1 – 6 from top to bottom are: SYST, RPS, STAT, DUPLX, SPEED, and PoE. Underneath the LED indicators and labeled 7 in the figure is the mode button. Above the switchports and labeled 8 in the figure are port LEDs.

The Mode button (7 in the figure) is used to toggle through port status, port duplex, port speed, and if supported, the Power over Ethernet (PoE) status of the port LEDs (8 in the figure).

1 SYST

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.

 

2 RPS

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.

 

3 STAT

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.

 

4 DUPLEX

Port Duplex LED

Indicates that 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.

 

5 SPEED

Port Speed LED

Indicates that 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 Mbps. If the LED is green, the port is operating at 100 Mbps. If the LED is blinking green, the port is operating at 1000 Mbps.

 

6 PoE

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 because of a fault. If the LED is amber, PoE for the port has been disabled.

Recovering from a System Crash

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

Type the help or ? at the boot loader prompt to view a list of available commands.

By default, the switch attempts to automatically boot up by using information in the BOOT environment variable. To view the path of the switch BOOT environment variable type the set command. Then, initialize the flash file system using the flash_init command to view the current files in flash, as shown in the output.

switch: set
BOOT=flash:/c2960-lanbasek9-mz.122-55.SE7/c2960-lanbasek9-mz.122-55.SE7.bin
(output omitted)
switch: flash_init
Initializing Flash...
flashfs[0]: 2 files, 1 directories
flashfs[0]: 0 orphaned files, 0 orphaned directories
flashfs[0]: Total bytes: 32514048
flashfs[0]: Bytes used: 11838464
flashfs[0]: Bytes available: 20675584
flashfs[0]: flashfs fsck took 10 seconds.
...done Initializing Flash.

After flash has finished initializing you can enter the dir flash: command to view the directories and files in flash, as shown in the output.

switch: dir flash: 
Directory of flash:/
    2  -rwx  11834846                 c2960-lanbasek9-mz.150-2.SE8.bin
    3  -rwx  2072                     multiple-fs

Enter the BOOT=flash command to change the BOOT environment variable path the switch uses to load the new IOS in flash. To verify the new BOOT environment variable path, issue the set command again. Finally, to load the new IOS type the boot command without any arguments, as shown in the output.

switch: BOOT=flash:c2960-lanbasek9-mz.150-2.SE8.bin
switch: set
BOOT=flash:c2960-lanbasek9-mz.150-2.SE8.bin
(output omitted)
switch: boot

The boot loader commands support initializing flash, formatting flash, installing a new IOS, changing the BOOT environment variable and recovery of lost or forgotten passwords.

Switch Management Access

To prepare a switch for remote management access, the switch must have a switch virtual interface (SVI) configured with an IPv4 address and subnet mask or an IPv6 address and a prefix length for IPv6. The SVI is a virtual interface, not a physical port on the switch. Keep in mind that to manage the switch from a remote network, the switch must be configured with a default gateway. This is very similar to configuring the IP address information on host devices.

Switch SVI Configuration Example

By default, the switch is configured to have its management controlled through VLAN 1. All ports are assigned to VLAN 1 by default. For security purposes, it is considered a best practice to use a VLAN other than VLAN 1 for the management VLAN, such as VLAN 99 in the example.

Step 1

Configure the Management Interface

From VLAN interface configuration mode, an IPv4 address and subnet mask is applied to the management SVI of the switch. Specifically, SVI VLAN 99 will be assigned the 172.17.99.11/24 IPv4 address and the 2001:db8:acad:99::1/64 IPv6 address as shown.

Note: The SVI for VLAN 99 will not appear as “up/up” until VLAN 99 is created and there is a device connected to a switch port associated with VLAN 99.

Note: The switch may need to be configured for IPv6. For example, before you can configure IPv6 addressing on a Cisco Catalyst 2960 running IOS version 15.0, you will need to enter the global configuration command sdm prefer dual-ipv4-and-ipv6 default and then reload the switch.

TaskIOS CommandsEnter global configuration mode.S1# configure terminalEnter interface configuration mode for the SVI.S1(config)# interface vlan 99Configure the management interface IPv4 address.S1(config-if)# ip address 172.17.99.11 255.255.255.0Configure the management interface IPv6 addressS1(config-if)# ipv6 address 2001:db8:acad:99::1/64Enable the management interface.S1(config-if)# no shutdownReturn to the privileged EXEC mode.S1(config-if)# endSave the running config to the startup config.S1# copy running-config startup-config
Task IOS Commands
Enter global configuration mode.
S1# configure terminal
Enter interface configuration mode for the SVI.
S1(config)# interface vlan 99
Configure the management interface IPv4 address.
S1(config-if)# ip address 172.17.99.11 255.255.255.0
Configure the management interface IPv6 address
S1(config-if)# ipv6 address 2001:db8:acad:99::11/64
Enable the management interface.
S1(config-if)# no shutdown
Return to the privileged EXEC mode.
S1(config-if)# end
Save the running config to the startup config.
S1# copy running-config startup-config

Step 2

Configure the Default Gateway

The switch should be configured with a default gateway if it will be managed remotely from networks that are not directly connected.

Note: Because, it will receive its default gateway information from a router advertisement (RA) message, the switch does not require an IPv6 default gateway.

Table caption
Task IOS Commands
Enter global configuration mode.
S1# configure terminal
Configure the default gateway for the switch.
S1(config)# ip default-gateway 172.17.99.1
Return to the privileged EXEC mode.
S1(config)# end
Save the running config to the startup config.
S1# copy running-config startup-config

Step 3

Verify Configuration

The show ip interface brief and show ipv6 interface brief commands are useful for determining the status of both physical and virtual interfaces. The output shown confirms that interface VLAN 99 has been configured with an IPv4 and IPv6 address.

Note: An IP address applied to the SVI is only for remote management access to the switch; this does not allow the switch to route Layer 3 packets.

S1# show ip interface brief
Interface     IP-Address     OK? Method   Status    Protocol
Vlan99        172.17.99.11   YES manual   down      down
(output omitted)
S1# show ipv6 interface brief
Vlan99                 [down/down]
    FE80::C27B:BCFF:FEC4:A9C1
    2001:DB8:ACAD:99::11
(output omitted)


 

Configure Switch Ports