To start your switch, you need to follow the procedures in the getting started guide or the hardware installation guide for installing and powering on the switch and setting up the initial switch configuration (IP address, subnet mask, default gateway, secret and Telnet passwords, and so forth).

The boot loader software performs the normal boot process and includes these activities:

• Locates the bootable (base) package in the bundle or installed package set.
• Performs low-level CPU initialization. It initializes the CPU registers, which control where physical memory is mapped, its quantity, its speed, and so forth.
• Performs power-on self-test (POST) for the CPU subsystem and tests the system DRAM.
• Initializes the file systems on the system board.
• Loads a default operating system software image into memory and boots up the switch.

The boot loader provides access to the flash file systems before the operating system is loaded. Normally, the boot loader is used only to load, decompress, and start the operating system. After the boot loader gives the operating system control of the CPU, the boot loader is not active until the next system reset or power-on.

The boot loader also provides trap-door access into the system if the operating system has problems serious enough that it cannot be used. The trap-door operation provides enough access to the system so that if it is necessary, you can format the flash file system, reinstall the operating system software image by using the Xmodem Protocol, recover from a lost or forgotten password, and finally restart the operating system.

Before you can assign switch information, make sure that you have connected a PC or terminal to the console port or a PC to the Ethernet management port, and make sure you have configured the PC or terminal-emulation software baud rate and character format to match that of the switch console port settings:

• Baud rate default is 9600.
• Data bits default is 8.

  Note	If the data bits option is set to 8, set the parity option to none.

• Stop bits default is 2 (minor).
• Parity settings default is none.

You can assign IP information through the switch setup program, through a DHCP server, or manually.

Use the switch setup program if you want to be prompted for specific IP information. With this program, you can also configure a hostname and an enable secret password.

It gives you the option of assigning a Telnet password (to provide security during remote management) and configuring your switch as a command or member switch of a cluster or as a standalone switch.

The switch stack is managed through a single IP address. The IP address is a system-level setting and is not specific to the stack master or to any other stack member. You can still manage the stack through the same IP address even if you remove the stack master or any other stack member from the stack, provided there is IP connectivity.

Note	Stack members retain their IP address when you remove them from a switch stack. To avoid a conflict by having two devices with the same IP address in your network, change the IP address of the switch that you removed from the switch stack.

Use a DHCP server for centralized control and automatic assignment of IP information after the server is configured.

Note	If you are using DHCP, do not respond to any of the questions in the setup program until the switch receives the dynamically assigned IP address and reads the configuration file.

If you are an experienced user familiar with the switch configuration steps, manually configure the switch. Otherwise, use the setup program described in the Boot Process section.

DHCP provides configuration information to Internet hosts and internetworking devices. This protocol consists of two components: one for delivering configuration parameters from a DHCP server to a device and an operation for allocating network addresses to devices. DHCP is built on a client-server model, in which designated DHCP servers allocate network addresses and deliver configuration parameters to dynamically configured devices. The switch can act as both a DHCP client and a DHCP server.

During DHCP-based autoconfiguration, your switch (DHCP client) is automatically configured at startup with IP address information and a configuration file.

With DHCP-based autoconfiguration, no DHCP client-side configuration is needed on your switch. However, you need to configure the DHCP server for various lease options associated with IP addresses.

If you want to use DHCP client autoconfiguration, you need to configure a Trivial File Transfer Protocol (TFTP) server to fetch the configuration file. The DHCP client then applies the new configuration file to its running configuration.

Note	If the new configuration is downloaded to a switch that already has a configuration, the downloaded configuration is appended to the configuration file stored on the switch. (Any existing configuration is not overwritten by the downloaded one.)

Note	We recommend a redundant connection between a switch stack and the DHCP, DNS, and TFTP servers. This is to help ensure that these servers remain accessible in case one of the connected stack members is removed from the switch stack.

The DHCP server for your switch can be on the same LAN or on a different LAN than the switch. If the DHCP server is running on a different LAN, you should configure a DHCP relay device between your switch and the DHCP server. A relay device forwards broadcast traffic between two directly connected LANs. A router does not forward broadcast packets, but it forwards packets based on the destination IP address in the received packet.

DHCP-based autoconfiguration replaces the BOOTP client functionality on your switch.

You can use the DHCP image upgrade features to configure a DHCP server to download both a new image and a new configuration file to one or more switches in a network. Simultaneous image and configuration upgrade for all switches in the network helps ensure that each new switch added to a network are synchronous with the network.

There are two types of DHCP image upgrades: DHCP autoconfiguration and DHCP auto-image update.

Follow these guidelines if you are configuring a device as a DHCP server:

• You should configure the DHCP server with reserved leases that are bound to each switch by the switch hardware address.
• If you want the switch to receive IP address information, you must configure the DHCP server with these lease options:
  • IP address of the client (required)
  • Subnet mask of the client (required)
  • DNS server IP address (optional)
  • Router IP address (default gateway address to be used by the switch) (required)
• If you want the switch to receive the configuration file from a TFTP server, you must configure the DHCP server with these lease options:
  • TFTP server name (required)
  • Boot filename (the name of the configuration file that the client needs) (recommended)
  • Hostname (optional)
• Depending on the settings of the DHCP server, the switch can receive IP address information, the configuration file, or both.
• If you do not configure the DHCP server with the lease options described previously, it replies to client requests with only those parameters that are configured. If the IP address and the subnet mask are not in the reply, the switch is not configured. If the router IP address or the TFTP server name are not found, the switch might send broadcast, instead of unicast, TFTP requests. Unavailability of other lease options does not affect autoconfiguration.
• The switch can act as a DHCP server. By default, the Cisco IOS DHCP server and relay agent features are enabled on your switch but are not configured.

Depending on the availability of the IP address and the configuration filename in the DHCP reserved lease, the switch obtains its configuration information in these ways:

• The IP address and the configuration filename is reserved for the switch and provided in the DHCP reply (one-file read method). The switch receives its IP address, subnet mask, TFTP server address, and the configuration filename from the DHCP server. The switch sends a unicast message to the TFTP server to retrieve the named configuration file from the base directory of the server and upon receipt, it completes its boot up process.
• The IP address and the configuration filename is reserved for the switch, but the TFTP server address is not provided in the DHCP reply (one-file read method). The switch receives its IP address, subnet mask, and the configuration filename from the DHCP server. The switch sends a broadcast message to a TFTP server to retrieve the named configuration file from the base directory of the server, and upon receipt, it completes its boot-up process.
• Only the IP address is reserved for the switch and provided in the DHCP reply. The configuration filename is not provided (two-file read method). The switch receives its IP address, subnet mask, and the TFTP server address from the DHCP server. The switch sends a unicast message to the TFTP server to retrieve the network-confg or cisconet.cfg default configuration file. (If the network-confg file cannot be read, the switch reads the cisconet.cfg file.) The default configuration file contains the hostnames-to-IP-address mapping for the switch. The switch fills its host table with the information in the file and obtains its hostname. If the hostname is not found in the file, the switch uses the hostname in the DHCP reply. If the hostname is not specified in the DHCP reply, the switch uses the default Switch as its hostname. After obtaining its hostname from the default configuration file or the DHCP reply, the switch reads the configuration file that has the same name as its hostname (hostname-confg or hostname.cfg, depending on whether network-confg or cisconet.cfg was read earlier) from the TFTP server. If the cisconet.cfg file is read, the filename of the host is truncated to eight characters. If the switch cannot read the network-confg, cisconet.cfg, or the hostname file, it reads the router-confg file. If the switch cannot read the router-confg file, it reads the ciscortr.cfg file.

Note	The switch broadcasts TFTP server requests if the TFTP server is not obtained from the DHCP replies, if all attempts to read the configuration file through unicast transmissions fail, or if the TFTP server name cannot be resolved to an IP address.

With a normally operating switch, you enter the boot loader mode only through the console connection. Unplug the switch power cord, then reconnect the power cord. Hold down the MODE button until you see the boot loader switch prompt

The switch boot loader software provides support for nonvolatile environment variables, which can be used to control how the boot loader or any other software running on the system, functions. Boot loader environment variables are similar to environment variables that can be set on UNIX or DOS systems.

Environment variables that have values are stored in flash memory outside of the flash file system.

Each line in these files contains an environment variable name and an equal sign followed by the value of the variable. A variable has no value if it is not present; it has a value if it is listed even if the value is a null string. A variable that is set to a null string (for example, “ ”) is a variable with a value. Many environment variables are predefined and have default values.

You can change the settings of the environment variables by accessing the boot loader or by using Cisco IOS commands. Under normal circumstances, it is not necessary to alter the setting of the environment variables.

You can schedule a reload of the software image to occur on the switch at a later time (for example, late at night or during the weekend when the switch is used less), or you can synchronize a reload network-wide (for example, to perform a software upgrade on all switches in the network).

Note	A scheduled reload must take place within approximately 24 days.

You have these reload options:

• Reload of the software to take affect in the specified minutes or hours and minutes. The reload must take place within approximately 24 hours. You can specify the reason for the reload in a string up to 255 characters in length.
• Reload of the software to take place at the specified time (using a 24-hour clock). If you specify the month and day, the reload is scheduled to take place at the specified time and date. If you do not specify the month and day, the reload takes place at the specified time on the current day (if the specified time is later than the current time) or on the next day (if the specified time is earlier than the current time). Specifying 00:00 schedules the reload for midnight.

The reload command halts the system. If the system is not set to manually boot up, it reboots itself.

If your switch is configured for manual booting, do not reload it from a virtual terminal. This restriction prevents the switch from entering the boot loader mode and then taking it from the remote user’s control.

If you modify your configuration file, the switch prompts you to save the configuration before reloading. During the save operation, the system requests whether you want to proceed with the save if the CONFIG_FILE environment variable points to a startup configuration file that no longer exists. If you proceed in this situation, the system enters setup mode upon reload.

To cancel a previously scheduled reload, use the reload cancel privileged EXEC command.

1.    configure terminal


2.    ip dhcp pool poolname


3.    boot filename


4.    network network-number mask prefix-length


5.    default-router address


6.    option 150 address


7.    exit


8.    tftp-server flash:filename.text


9.    interface interface-id


10.    no switchport


11.    ip address address mask


12.    end

Switch# configure terminal

Switch(config)# ip dhcp pool pool

Switch(dhcp-config)# boot config-boot.text

Switch(dhcp-config)# network 10.10.10.0 255.255.255.0

Switch(dhcp-config)# default-router 10.10.10.1

Switch(dhcp-config)# option 150 10.10.10.1

Switch(dhcp-config)# exit

Switch(config)# tftp-server flash:config-boot.text

Switch(config)# interface gigabitethernet1/0/4

Switch(config-if)# no switchport

Switch(config-if)# ip address 10.10.10.1 255.255.255.0

Switch(config-if)# end

1.    configure terminal


2.    ip dhcp pool poolname


3.    boot filename


4.    network network-number mask prefix-length


5.    default-router address


6.    option 150 address


7.    option 125 hex


8.    copy tftp flash filename.txt


9.    copy tftp flash imagename.bin


10.    exit


11.    tftp-server flash: config.text


12.    tftp-server flash: imagename.bin


13.    tftp-server flash: filename.txt


14.    interface interface-id


15.    no switchport


16.    ip address address mask


17.    end


18.    copy running-config startup-config

Switch# configure terminal

Switch(config)# ip dhcp pool pool1

Switch(dhcp-config)# boot config-boot.text

Switch(dhcp-config)# network 10.10.10.0 255.255.255.0

Switch(dhcp-config)# default-router 10.10.10.1

Switch(dhcp-config)# option 150 10.10.10.1

Switch(dhcp-config)# option 125 hex 0000.0009.0a05.08661.7574.6f69.6e73.7461.6c6c.5f64.686370

Switch(config)# copy tftp flash image.bin

Switch(config)# copy tftp flash image.bin

Switch(dhcp-config)# exit

Switch(config)# tftp-server flash:config-boot.text

Switch(config)# tftp-server flash:image.bin

Switch(config)# tftp-server flash:boot-config.text

Switch(config)# interface gigabitEthernet1/0/4

Switch(config-if)# no switchport

Switch(config-if)# ip address 10.10.10.1 255.255.255.0

Switch(config-if)# end

Switch(config-if)# end

Note	You should only configure and enable the Layer 3 interface. Do not assign an IP address or DHCP-based autoconfiguration with a saved configuration.

1.    configure terminal


2.    boot host dhcp


3.    boot host retry timeout timeout-value


4.    banner config-save ^C warning-message ^C


5.    end


6.    show boot

Switch# configure terminal

Switch(conf)# boot host dhcp

Switch(conf)# boot host retry timeout 300

Switch(conf)# banner config-save ^C Caution - Saving Configuration File to NVRAM May Cause You to No longer Automatically Download Configuration Files at Reboot^C

Switch(config-if)# end

Switch# show boot

1.    configure terminal


2.    interface vlan vlan-id


3.    ip address ip-address subnet-mask


4.    exit


5.    ip default-gateway ip-address


6.    end


7.    show interfaces vlan vlan-id


8.    show ip redirects

Switch# configure terminal

Switch(config)# interface vlan 99

Switch(config-vlan)# ip address 10.10.10.2 255.255.255.0

Switch(config-vlan)# exit

Switch(config)# ip default-gateway 10.10.10.1

Switch(config)# end

Switch# show interfaces vlan 99

Switch# show ip redirects

The default NVRAM buffer size is 512 KB. In some cases, the configuration file might be too large to save to NVRAM. Typically, this occurs when you have many switches in a switch stack. You can configure the size of the NVRAM buffer to support larger configuration files. The new NVRAM buffer size is synced to all current and new member switches.

Note	After you configure the NVRAM buffer size, reload the switch or switch stack. When you add a switch to a stack and the NVRAM size differs, the new switch syncs with the stack and reloads automatically.

1.    configure terminal


2.    boot buffersize size


3.    end


4.    show boot

Switch# configure terminal

Switch(config)# boot buffersize 524288

Switch(config)# end

Switch# show boot