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Assigning the Switch
IP Address and Default Gateway
Finding Feature
Information
Your software release
may not support all the features documented in this module. For the latest
caveats and feature information, see Bug Search Tool and the release notes for
your platform and software release. To find information about the features
documented in this module, and to see a list of the releases in which each
feature is supported, see the feature information table at the end of this
module.
Use Cisco Feature
Navigator to find information about platform support and Cisco software image
support. To access Cisco Feature Navigator, go to
http://www.cisco.com/go/cfn.
An account on Cisco.com is not required.
Information About Performing Switch Setup Configuration
Review the sections in this module before performing your initial switch configuration tasks that include IP address assignments and DHCP autoconfiguration.
Switches Information Assignment
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.
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.
Default Switch
Information
Table 1. Default Switch
Information
Feature
Default
Setting
IP address and
subnet mask
No IP address
or subnet mask are defined.
Default
gateway
No default
gateway is defined.
Enable secret
password
No password is
defined.
Hostname
The
factory-assigned default hostname is
Switch.
Telnet
password
No password is
defined.
Cluster
command switch functionality
Disabled.
Cluster name
No cluster
name is defined.
DHCP-Based
Autoconfiguration Overview
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 to relay the configuration file location on the network, you might also
need to configure a Trivial File Transfer Protocol (TFTP) server and a Domain
Name System (DNS) server.
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.
DHCP Client Request
Process
When you boot up your
switch,
the DHCP client is invoked and requests configuration information from a DHCP
server when the configuration file is not present on the
switch.
If the configuration file is present and the configuration includes the
ip address dhcp
interface configuration command on specific routed interfaces, the DHCP client
is invoked and requests the IP address information for those interfaces.
This is the sequence
of messages that are exchanged between the DHCP client and the DHCP server.
The client,
Switch
A, broadcasts a DHCPDISCOVER message to locate a DHCP server. The DHCP server
offers configuration parameters (such as an IP address, subnet mask, gateway IP
address, DNS IP address, a lease for the IP address, and so forth) to the
client in a DHCPOFFER unicast message.
In a DHCPREQUEST
broadcast message, the client returns a formal request for the offered
configuration information to the DHCP server. The formal request is broadcast
so that all other DHCP servers that received the DHCPDISCOVER broadcast message
from the client can reclaim the IP addresses that they offered to the client.
The DHCP server
confirms that the IP address has been allocated to the client by returning a
DHCPACK unicast message to the client. With this message, the client and server
are bound, and the client uses configuration information received from the
server. The amount of information the
switch
receives depends on how you configure the DHCP server.
If the configuration
parameters sent to the client in the DHCPOFFER unicast message are invalid (a
configuration error exists), the client returns a DHCPDECLINE broadcast message
to the DHCP server.
The DHCP server sends
the client a DHCPNAK denial broadcast message, which means that the offered
configuration parameters have not been assigned, that an error has occurred
during the negotiation of the parameters, or that the client has been slow in
responding to the DHCPOFFER message (the DHCP server assigned the parameters to
another client).
A DHCP client might
receive offers from multiple DHCP or BOOTP servers and can accept any of the
offers; however, the client usually accepts the first offer it receives. The
offer from the DHCP server is not a guarantee that the IP address is allocated
to the client; however, the server usually reserves the address until the
client has had a chance to formally request the address. If the
switch
accepts replies from a BOOTP server and configures itself, the
switch
broadcasts, instead of unicasts, TFTP requests to obtain the
switch
configuration file.
The DHCP hostname option allows a group of
switches
to obtain hostnames and a standard configuration from the central management
DHCP server. A client (switch)
includes in its DCHPDISCOVER message an option 12 field used to request a
hostname and other configuration parameters from the DHCP server. The
configuration files on all clients are identical except for their DHCP-obtained
hostnames.
If a client has a default hostname (the
hostname name global configuration command is not
configured or the
no hostname
global configuration command is entered to remove the hostname), the DHCP
hostname option is not included in the packet when you enter the
ip address dhcp
interface configuration command. In this case, if the client receives the DCHP
hostname option from the DHCP interaction while acquiring an IP address for an
interface, the client accepts the DHCP hostname option and sets the flag to
show that the system now has a hostname configured.
DHCP-based
Autoconfiguration and Image Update
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 receives the same
image and configuration.
There are two types of
DHCP image upgrades: DHCP autoconfiguration and DHCP auto-image update.
Restrictions for
DHCP-based Autoconfiguration
The DHCP-based
autoconfiguration with a saved configuration process stops if there is not at
least one Layer 3 interface in an up state without an assigned IP address in
the network.
Unless you
configure a timeout, the DHCP-based autoconfiguration with a saved
configuration feature tries indefinitely to download an IP address.
The auto-install
process stops if a configuration file cannot be downloaded or if the
configuration file is corrupted.
The configuration
file that is downloaded from TFTP is merged with the existing configuration in
the running configuration but is not saved in the NVRAM unless you enter the
write memory or
copy running-configuration
startup-configuration privileged EXEC command. If the downloaded
configuration is saved to the startup configuration, the feature is not
triggered during subsequent system restarts.
DHCP Autoconfiguration
DHCP autoconfiguration downloads a configuration file to one or more switches in your network from a DHCP server. The downloaded configuration file becomes the running configuration of the switch. It does not over write the bootup configuration saved in the flash, until you reload the switch.
DHCP Auto-Image
Update
You can use DHCP
auto-image upgrade with DHCP autoconfiguration to download both a configuration
and a new image to one or more
switches in your network. The
switch (or
switches) downloading the new configuration and
the new image can be blank (or only have a default factory configuration
loaded).
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.)
To enable a DHCP
auto-image update on the
switch, the TFTP server where the image and
configuration files are located must be configured with the correct option 67
(the configuration filename), option 66 (the DHCP server hostname) option 150
(the TFTP server address), and option 125 (description of the Cisco IOS image
file) settings.
After you install the
switch in your network, the auto-image update
feature starts. The downloaded configuration file is saved in the running
configuration of the
switch, and the new image is downloaded and
installed on the
switch. When you reboot the
switch, the configuration is stored in the
saved configuration on the
switch.
DHCP Server
Configuration Guidelines
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. (These
features are not operational.)
Purpose of the TFTP Server
Based on the DHCP server configuration, the switch attempts to download one or more configuration files from the TFTP server. If you configured the DHCP server to respond to
the switch with all the options required for IP connectivity to the TFTP server, and if you configured the DHCP server with a TFTP
server name, address, and configuration filename, the switch attempts to download the specified configuration file from the specified TFTP server.
If you did not specify the configuration filename, the TFTP server, or if the configuration file could not be downloaded,
the switch attempts to download a configuration file by using various combinations of filenames and TFTP server addresses. The files
include the specified configuration filename (if any) and these files: network-config, cisconet.cfg, hostname.config, or hostname.cfg, where hostname is the switch’s current hostname. The TFTP server addresses used include the specified TFTP server address (if any) and the broadcast address
(255.255.255.255).
For the switch to successfully download a configuration file, the TFTP server must contain one or more configuration files in its base directory.
The files can include these files:
The configuration file named in the DHCP reply (the actual switch configuration file).
The network-confg or the cisconet.cfg file (known as the default configuration files).
The router-confg or the ciscortr.cfg file (These files contain commands common to all switches. Normally, if the DHCP and TFTP servers are properly configured, these files are not accessed.)
If you specify the TFTP server name in the DHCP server-lease database, you must also configure the TFTP server name-to-IP-address
mapping in the DNS-server database.
If the TFTP server to be used is on a different LAN from the switch, or if it is to be accessed by the switch through the broadcast address (which occurs if the DHCP server response does not contain all the required information described
previously), a relay must be configured to forward the TFTP packets to the TFTP server. The preferred solution is to configure
the DHCP server with all the required information.
Purpose of the DNS Server
The DHCP server uses the DNS server to resolve the TFTP server name to an IP address. You must configure the TFTP server name-to-IP
address map on the DNS server. The TFTP server contains the configuration files for the switch.
You can configure the IP addresses of the DNS servers in the lease database of the DHCP server from where the DHCP replies
will retrieve them. You can enter up to two DNS server IP addresses in the lease database.
The DNS server can be on the same LAN or on a different LAN from the switch. If it is on a different LAN, the switch must be able to access it through a router.
Purpose of the Relay
Device
You must configure a
relay device, also referred to as a relay agent, when a switch sends broadcast
packets that require a response from a host on a different LAN. Examples of
broadcast packets that the switch might send are DHCP, DNS, and in some cases,
TFTP packets. You must configure this relay device to forward received
broadcast packets on an interface to the destination host.
If the relay device is a Cisco router, enable IP routing (ip routing global
configuration command), and configure helper addresses by using the
ip
helper-address interface configuration command.
Examples of
Configuring the Relay Device
Configure the router
interfaces as follows:
On interface
10.0.0.2:
router(config-if)# ip helper-address 20.0.0.2
router(config-if)# ip helper-address 20.0.0.3
router(config-if)# ip helper-address 20.0.0.4
On interface
20.0.0.1
router(config-if)# ip helper-address 10.0.0.1
Note
If the switch
is acting as the relay device, configure the interface as a routed port.
How to Obtain
Configuration Files
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.
Example of
DHCP-Based Autoconfiguration Network
A sample network for
retrieving IP information using DHCP-based autoconfiguration.
Table 2. DHCP Server
Configuration
Switch A
Switch B
Switch C
Switch D
Binding key
(hardware address)
00e0.9f1e.2001
00e0.9f1e.2002
00e0.9f1e.2003
00e0.9f1e.2004
IP address
10.0.0.21
10.0.0.22
10.0.0.23
10.0.0.24
Subnet mask
255.255.255.0
255.255.255.0
255.255.255.0
255.255.255.0
Router
address
10.0.0.10
10.0.0.10
10.0.0.10
10.0.0.10
DNS server
address
10.0.0.2
10.0.0.2
10.0.0.2
10.0.0.2
TFTP server
name
tftpserver
or 10.0.0.3
tftpserver
or 10.0.0.3
tftpserver
or 10.0.0.3
tftpserver
or 10.0.0.3
Boot
filename (configuration file) (optional)
switcha-confg
switchb-confg
switchc-confg
switchd-confg
Hostname
(optional)
switcha
switchb
switchc
switchd
Switch A reads its
configuration file as follows:
It obtains its IP address
10.0.0.21 from the DHCP server.
If no configuration
filename is given in the DHCP server reply, Switch A reads the network-confg
file from the base directory of the TFTP server.
It adds the contents of the
network-confg file to its host table.
It reads its host table by
indexing its IP address 10.0.0.21 to its hostname (switcha).
It reads the configuration
file that corresponds to its hostname; for example, it reads switch1-confg from
the TFTP server.
Switches B through
D retrieve their configuration files and IP addresses in the same way.
DNS Server
Configuration
The DNS server
maps the TFTP server name tftpserver to IP address 10.0.0.3.
TFTP Server
Configuration (on UNIX)
The TFTP server
base directory is set to /tftpserver/work/. This directory contains the
network-confg file used in the two-file read method. This file contains the
hostname to be assigned to the switch based on its IP address. The base
directory also contains a configuration file for each switch (switcha-confg,
switchb-confg, and so forth) as shown in this display:
prompt> cd /tftpserver/work/
prompt> 1s
network-confg
switcha-confg
switchb-confg
switchc-confg
switchd-confg
prompt> cat network-confg
ip host switcha 10.0.0.21
ip host switchb 10.0.0.22
ip host switchc 10.0.0.23
ip host switchd 10.0.0.24
DHCP Client
Configuration
No configuration
file is present on Switch A through Switch D.
Configuration
Explanation
In the figure,
DHCP-based autoconfiguration network, the Switch A reads its configuration file
as follows:
It obtains its IP address
10.0.0.21 from the DHCP server.
If no configuration
filename is given in the DHCP server reply, Switch A reads the network-confg
file from the base directory of the TFTP server.
It adds the contents of the
network-confg file to its host table.
It reads its host table by
indexing its IP address 10.0.0.21 to its hostname (switcha).
It reads the configuration
file that corresponds to its hostname; for example, it reads switch1-confg from
the TFTP server.
Switches B through
D retrieve their configuration files and IP addresses in the same way.
How to Control Environment Variables
With a normally operating switch, you enter the boot loader mode only through the console connection configured for 9600 bps. Unplug the switch power cord, and press the Mode button while reconnecting the power cord. You can release the Mode button after all the amber system LEDs turn on and remain solid. The boot loader switch prompt then appears.
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, operates. 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.
Common Environment
Variables
This table describes the function of the most common environment
variables.
Table 3. Common Environment
Variables
Variable
Boot Loader
Command
Cisco IOS
Global Configuration Command
BOOT
set BOOT filesystem:/ file-url
...
A
semicolon-separated list of executable files to try to load and execute when
automatically booting.
boot system {filesystem: /file-url ... |
switch {number |
all }}
Specifies the
Cisco IOS image to load during the next boot cycle and the stack members on
which the image is loaded. This command changes the setting of the BOOT
environment variable.
The package
provisioning file, also referred to as the
packages.conf file, is used by the system to determine which
software packages to activate during boot up.
When
booting in installed mode, the package provisioning file specified in the
boot command
is used to determine which packages to activate. For example
boot
flash:packages.conf .
When
booting in bundle mode, the package provisioning file contained in the booted
bundle is used to activate the packages included in the bundle. For example,
boot
flash:image.bin .
MANUAL_BOOT
set MANUAL_BOOT yes
Decides
whether the switch automatically or manually boots.
Valid values
are 1, yes, 0, and no. If it is set to no or 0, the boot loader attempts to
automatically boot up the system. If it is set to anything else, you must
manually boot up the switch from the boot loader mode.
boot manual
Enables
manually booting the switch during the next boot cycle and changes the setting
of the MANUAL_BOOT environment variable.
The next time
you reboot the system, the switch is in boot loader mode. To boot up the
system, use the
boot flash: filesystem:/ file-url boot loader command, and specify the name
of the bootable image.
CONFIG_FILE
set CONFIG_FILE flash:/ file-url
Changes the
filename that Cisco IOS uses to read and write a nonvolatile copy of the system
configuration.
boot config-file flash:/ file-url
Specifies the
filename that Cisco IOS uses to read and write a nonvolatile copy of the system
configuration. This command changes the CONFIG_FILE environment variable.
Enables a
break to the auto-boot cycle. You have 5 seconds to enter the
break
command.
Environment Variables for TFTP
When the switch is connected to a PC through the Ethernet management port, you can download or upload a configuration file
to the boot loader by using TFTP. Make sure the environment variables in this table are configured.
Table 4. Environment Variables for TFTP
Variable
Description
MAC_ADDR
Specifies the MAC address of the switch.
Note
We recommend that you do not modify this variable.
However, if you modify this variable after the boot loader is up or the value is different from the saved value, enter this
command before using TFTP.
IP_ADDR
Specifies the IP address and the subnet mask for the associated IP subnet of the switch.
DEFAULT_ROUTER
Specifies the IP address and subnet mask of the default gateway.
Scheduled Reload of the Software Image
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).
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.
How to Perform
Switch
Setup Configuration
Using DHCP to download
a new image and a new configuration to a
switch
requires that you configure at least two
switches.
One
switch
acts as a DHCP and TFTP server and the second
switch
(client) is configured to download either a new configuration file or a new
configuration file and a new image file.
This task describes how to configure DHCP autoconfiguration of the TFTP and DHCP settings on an existing switch in the network so that it can support the autoconfiguration of a new switch.
Procedure
Command or Action
Purpose
Step 1
configure terminal
Example:
Switch# configure terminal
Enters global configuration mode.
Step 2
ip dhcp pool poolname
Example:
Switch(config)# ip dhcp pool pool
Creates a name for the DHCP server address pool, and enters DHCP pool configuration mode.
Step 3
boot filename
Example:
Switch(dhcp-config)# boot config-boot.text
Specifies the name of the configuration file that is used as a boot image.
Specifies the subnet network number and mask of the DHCP address pool.
Note
The prefix length specifies the number of bits that comprise the address prefix. The prefix is an alternative way of specifying
the network mask of the client. The prefix length must be preceded by a forward slash (/).
Step 5
default-router address
Example:
Switch(dhcp-config)# default-router 10.10.10.1
Specifies the IP address of the default router for a DHCP client.
Specifies the configuration file on the TFTP server.
Step 9
interface interface-id
Example:
Switch(config)# interface gigabitethernet1/0/4
Specifies the address of the client that will receive the configuration file.
Step 10
no switchport
Example:
Switch(config-if)# no switchport
Puts the interface into Layer 3 mode.
Step 11
ip address address mask
Example:
Switch(config-if)# ip address 10.10.10.1 255.255.255.0
Specifies the IP address and mask for the interface.
Step 12
end
Example:
Switch(config-if)# end
Returns to privileged EXEC mode.
Configuring DHCP
Auto-Image Update (Configuration File and Image)
This task describes
DHCP autoconfiguration to configure TFTP and DHCP settings on an existing
switch to support the installation of a new
switch.
Before you begin
You must first
create a text file (for example, autoinstall_dhcp) that will be uploaded to the
switch. In the text file, put the name of
the image that you want to download (forexample,
c3750e-ipservices-mz.122-44.3.SE.tarc3750x-ipservices-mz.122-53.3.SE2.tar).
This image must be a tar and not a bin file.
Procedure
Command or Action
Purpose
Step 1
configure terminal
Example:
Switch# configure terminal
Enters global
configuration mode.
Step 2
ip dhcp pool poolname
Example:
Switch(config)# ip dhcp pool pool1
Creates a name
for the DHCP server address pool and enter DHCP pool configuration mode.
Step 3
boot filename
Example:
Switch(dhcp-config)# boot config-boot.text
Specifies the
name of the file that is used as a boot image.
Specifies the
subnet network number and mask of the DHCP address pool.
Note
The prefix
length specifies the number of bits that comprise the address prefix. The
prefix is an alternative way of specifying the network mask of the client. The
prefix length must be preceded by a forward slash (/).
Step 5
default-router address
Example:
Switch(dhcp-config)# default-router 10.10.10.1
Specifies the IP
address of the default router for a DHCP client.
Specifies the
text file that contains the name of the image file to download
Step 14
interface interface-id
Example:
Switch(config)# interface gigabitEthernet1/0/4
Specifies the
address of the client that will receive the configuration file.
Step 15
no switchport
Example:
Switch(config-if)# no switchport
Puts the
interface into Layer 3 mode.
Step 16
ip address address
mask
Example:
Switch(config-if)# ip address 10.10.10.1 255.255.255.0
Specifies the
IP address and mask for the interface.
Step 17
end
Example:
Switch(config-if)# end
Returns to
privileged EXEC mode.
Step 18
copy running-config startup-config
Example:
Switch(config-if)# end
(Optional)
Saves your entries in the configuration file.
Configuring the Client to Download Files from DHCP Server
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.
Procedure
Command or Action
Purpose
Step 1
configure terminal
Example:
Switch# configure terminal
Enters global configuration mode.
Step 2
boot host dhcp
Example:
Switch(conf)# boot host dhcp
Enables autoconfiguration with a saved configuration.
Step 3
boot host retry timeout timeout-value
Example:
Switch(conf)# boot host retry timeout 300
(Optional) Sets the amount of time the system tries to download a configuration file.
Note
If you do not set a timeout, the system will try indefinitely to obtain an IP address from the DHCP server.
Step 4
banner config-save ^C warning-message^C
Example:
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
(Optional) Creates warning messages to be displayed when you try to save the configuration file to NVRAM.
Step 5
end
Example:
Switch(config-if)# end
Returns to privileged EXEC mode.
Step 6
show boot
Example:
Switch# show boot
Verifies the configuration.
Manually Assigning
IP Information to Multiple SVIs
This task describes
how to manually assign IP information to multiple switched virtual interfaces
(SVIs):
Procedure
Command or Action
Purpose
Step 1
configure terminal
Example:
Switch# configure terminal
Enters global
configuration mode.
Step 2
interface vlan vlan-id
Example:
Switch(config)# interface vlan 99
Enters interface
configuration mode, and enters the VLAN to which the IP information is
assigned. The range is 1 to 4094.
Step 3
ip address ip-address
subnet-mask
Example:
Switch(config-vlan)# ip address 10.10.10.2 255.255.255.0
Enters the IP
address and subnet mask.
Step 4
exit
Example:
Switch(config-vlan)# exit
Returns to
global configuration mode.
Step 5
ip default-gateway ip-address
Example:
Switch(config)# ip default-gateway 10.10.10.1
Enters the IP
address of the next-hop router interface that is directly connected to the
switch where a default gateway is being
configured. The default gateway receives IP packets with unresolved destination
IP addresses from the
switch.
Once the default
gateway is configured, the
switch has connectivity to the remote
networks with which a host needs to communicate.
Note
When your
switch is configured to route with IP, it
does not need to have a default gateway set.
Note
The
switch capwap relays on default-gateway
configuration to support routed access point join the
switch.
Step 6
end
Example:
Switch(config)# end
Returns to
privileged EXEC mode.
Step 7
show interfaces vlan vlan-id
Example:
Switch# show interfaces vlan 99
Verifies the
configured IP address.
Step 8
show ip redirects
Example:
Switch# show ip redirects
Verifies the
configured default gateway.
Modifying the Switch Startup Configuration
Default Boot
Configuration
Feature
Default Setting
Operating system software
image
The switch
attempts to automatically boot up the system using information in the BOOT
environment variable. If the variable is not set, the switch attempts to load
and execute the first executable image it can by performing a recursive,
depth-first search throughout the flash file system.
The Cisco
IOS image is stored in a directory that has the same name as the image file
(excluding the .bin extension).
In a
depth-first search of a directory, each encountered subdirectory is completely
searched before continuing the search in the original directory.
Configuration file
Configured
switches use the
config.text file stored on the system board in flash memory.
A new
switch has no configuration file.
Specifying the
Filename to Read and Write the System Configuration
By default, the Cisco IOS software uses the config.text
file to read and write a nonvolatile copy of the system configuration. However,
you can specify a different filename, which will be loaded during the next boot
cycle.
Before you begin
Use a standalone
switch
for this task.
Procedure
Command or Action
Purpose
Step 1
configure terminal
Example:
Switch# configure terminal
Enters global
configuration mode.
Step 2
boot flash :/file-url
Example:
Switch(config)# boot flash:config.text
Specifies the
configuration file to load during the next boot cycle.
file-url—The path (directory) and the
configuration filename.
Filenames and
directory names are case-sensitive.
Step 3
end
Example:
Switch(config)# end
Returns to
privileged EXEC mode.
Step 4
show boot
Example:
Switch# show boot
Verifies your
entries.
The
boot
global configuration command changes the setting
of the CONFIG_FILE environment variable.
Step 5
copy running-config startup-config
Example:
Switch# copy running-config startup-config
(Optional) Saves
your entries in the configuration file.
Manually Booting the
Switch
By default, the
switch automatically boots up; however, you can configure it to manually boot
up.
Before you begin
Use a standalone
switch for this task.
Procedure
Command or Action
Purpose
Step 1
configure terminal
Example:
Switch# configure terminal
Enters global
configuration mode.
Step 2
boot manual
Example:
Switch(config)# boot manual
Enables the
switch to manually boot up during the next boot cycle.
Step 3
end
Example:
Switch(config)# end
Returns to
privileged EXEC mode.
Step 4
show boot
Example:
Switch# show boot
Verifies your
entries.
The
boot manual
global command changes the setting of the MANUAL_BOOT environment variable.
The next time
you reboot the system, the switch is in boot loader mode, shown by the
switch:
prompt. To boot up the system, use the
boot filesystem:/file-url boot loader command.
filesystem:—Uses flash: for the system board flash
device.
switch: boot flash:
For
file-url—Specifies the path (directory) and the
name of the bootable image.
Filenames and
directory names are case-sensitive.
Step 5
copy running-config startup-config
Example:
Switch# copy running-config startup-config
(Optional) Saves
your entries in the configuration file.
Booting a Specific Software
Image On a Switch Stack
By default, the switch attempts to automatically boot up the system
using information in the BOOT environment variable. If this variable is not
set, the switch attempts to load and execute the first executable image it can
by performing a recursive, depth-first search throughout the flash file system.
In a depth-first search of a directory, each encountered subdirectory is
completely searched before continuing the search in the original directory.
However, you can specify a specific image to boot up.
Procedure
Command or Action
Purpose
Step 1
configure terminal
Example:
Switch# configure terminal
Enters global
configuration mode.
Step 2
boot system switch
{number |
all }
Example:
Switch(config)# boot system switch 2 flash:cat3850-universalk9.SSA.03.08.83.EMD.150-8.83.EMD.bin
(Optional) For
switches in a stack, specifies the switch members on which the system image is
loaded during the next boot cycle:
Use
number to
specify a stack member. (Specify only one stack member.)
Use
all to
specify all stack members.
If you enter on a Catalyst 3750-X stack master or member, you can
only specify the switch image for other Catalyst 3750-X stack members.
If you enter on a Catalyst 3750-E stack master or member, you can
only specify the switch image for other Catalyst 3750-E stack members.
If you want to specify the image for a Catalyst 3750 switch, enter
this command on the Catalyst 3750 stack member.
Step 3
end
Example:
Switch(config)# end
Returns to
privileged EXEC mode.
Step 4
show boot system
Example:
Switch# show boot system
Verifies your
entries.
The
boot system
global command changes the setting of the BOOT environment variable.
During the next
boot cycle, the switch attempts to automatically boot up the system using
information in the BOOT environment variable.
Step 5
copy running-config startup-config
Example:
Switch# copy running-config startup-config
(Optional) Saves
your entries in the configuration file.
Controlling
Environment Variables
With a normally operating switch, you enter the boot loader mode only
through a switch console connection configured for 9600 b/s. Unplug the switch
power cord, and press the switch
Mode button while reconnecting the power cord. You can release the
Mode button a second or two after the LED above port 1 turns off.
Then the boot loader switch: prompt appears.
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, behaves. 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 listed in this
file; it has a value if it is listed in the file 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.
Environment variables store two kinds of data:
Data that controls
code, which does not read the Cisco IOS configuration file. For example, the
name of a boot loader helper file, which extends or patches the functionality
of the boot loader can be stored as an environment variable.
Data that controls
code, which is responsible for reading the Cisco IOS configuration file. For
example, the name of the Cisco IOS configuration file can be stored as an
environment variable.
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.
Note
For complete syntax and usage information for the boot loader
commands and environment variables, see the command reference for this release.
Table 5. Environment Variables
Variable
Boot Loader Command
Cisco IOS Global Configuration Command
BOOT
set BOOT filesystem :/ file-url ...
A semicolon-separated list of executable files to try to load and
execute when automatically booting. If the BOOT environment variable is not
set, the system attempts to load and execute the first executable image it can
find by using a recursive, depth-first search through the flash file system. If
the BOOT variable is set but the specified images cannot be loaded, the system
attempts to boot the first bootable file that it can find in the flash file
system.
boot system filesystem:/file-url
...
Specifies the Cisco IOS image to load during the next boot cycle.
This command changes the setting of the BOOT environment variable
MANUAL_BOOT
set MANUAL_BOOT yes
Decides whether the switch automatically or manually boots up.
Valid values are 1, yes, 0, and no. If it is set to no or 0, the
boot loader attempts to automatically boot up the system. If it is set to
anything else, you must manually boot up the switch from the boot loader mode.
boot manual
Enables manually booting up the switch during the next boot cycle
and changes the setting of the MANUAL_BOOT environment variable.
The next time you reboot the system, the switch is in boot loader
mode. To boot up the system, use the
boot flash: filesystem :/ file-url
boot loader command, and specify the name of the
bootable image.
CONFIG_FILE
set CONFIG_FILE flash: / file-url
boot config-file flash: / file-url
Specifies the filename that Cisco IOS uses to read and write a
nonvolatile copy of the system configuration. This command changes the
CONFIG_FILE environment variable.
This command is supported only on Catalyst 3750-E Catalyst
3750-X switches.
SWITCH_PRIORITY
set SWITCH_PRIORITY
stack-member-number
Changes the priority value of a stack member
switch stack-member-numberpriority priority- number
Changes the priority value of a stack member.
Note
This command is supported only on Catalyst 3750-E Catalyst
3750-X switches.
Scheduling a Reload
of the Software Image
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.
Configuring a Scheduled Reload
To configure your switch to reload the software image at a later time,
use one of these commands in privileged EXEC mode:
reload in
[hh :]mm [text]
This command schedules a reload of the software to take affect in
the specified minutes or hours and minutes. The reload must take place within
approximately 24 days. You can specify the reason for the reload in a string up
to 255 characters in length.
reload at
hh:mm
[month dayI day month
[text]
This command schedules a 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.
Note
Use the
at keyword only if the switch system clock has been set
(through Network Time Protocol (NTP), the hardware calendar, or manually). The
time is relative to the configured time zone on the switch. To schedule reloads
across several switches to occur simultaneously, the time on each switch must
be synchronized with NTP.
The
reload command halts the system. If the system is not set to
manually boot up, it reboots itself. Use the
reload command after you save the switch configuration
information to the startup configuration (copy running-config
startup-config).
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 thereby 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.
This example shows how to reload the software on the switch on the
current day at 7:30 p.m:
Switch# reload at 19:30
Reload scheduled for 19:30:00 UTC Wed Jun 5 1996 (in 2 hours and 25 minutes)
Proceed with reload? [confirm]
This example shows how to reload the software on the switch at a
future time:
Switch# reload at 02:00 jun 20
Reload scheduled for 02:00:00 UTC Thu Jun 20 1996 (in 344 hours and 53 minutes)
Proceed with reload? [confirm]
To cancel a previously scheduled reload, use the
reload cancel privileged EXEC command
Displaying Scheduled Reload Information
To display information about a previously scheduled reload or to find
out if a reload has been scheduled on the switch, use the
show reload privileged EXEC command.
It displays reload information including the time the reload is
scheduled to occur and the reason for the reload (if it was specified when the
reload was scheduled).
Boot Loader Upgrade
and Image Verification for the FIPS Mode of Operation
To operate in the FIPS mode, complete these steps:
Enable the FIPS mode on the switch.To enable the FIPS mode, enter
the
fips authorization-keyauthorization-key global configuration command. To disable
the FIPS mode, use the no version of the command.
Use signed and validated images. Cisco IOS Release 15.2(1)E
supports an updated boot loader that can validate the Cisco IOS image signature
only in the FIPS mode of operation.
Note
Ensure that the power is not turned off while updating the boot
loader. If the power is turned off during the update, you will have to replace
the switch by using a Return Merchandise Authorization (RMA) license.
Table 4-6 describes upgrade and downgrade scenarios using different
images and using the FIPS mode or non-FIPS mode:
Table 6. Upgrade and Downgrade Scenarios Relating to FIPS Certified
Images
Upgrade/ Downgrade Scenario
Action
Status or Result
Upgrade from an image that is in the FIPS mode to a Cisco IOS
Release 15.2(1)E image in the FIPS mode.
Boot with the Cisco IOS Release 15.2(1)E image.
The boot loader is
upgraded.
The image
signature is verified.
The following
message appears in the boot sequence: “Image passed digital signature
verification.”
Note
If you upload a corrupt or unsigned image, the following
message appears during boot up: “Image verification failed.”
Upgrade from a switch that is in the non-FIPS mode to a Cisco
IOS Release 15.2(1)E image in the FIPS mode
Configure the fips
authorization- key authorization-key global configuration command
Reload the switch
for the FIPS key to be operational. By default, the switch automatically boots
up; however, if you have configured it to boot up manually, you have to
initiate the reboot.
After the boot
loader is upgraded, boot with the Cisco IOS Release 15.2(1)E image.
The boot loader is
upgraded.
The image
signature is verified.
Note
If you upload a corrupt or unsigned image, the following
message appears during boot up: “Image verification failed.
Upgrade to Cisco IOS Release 15.2(1)E in the non-FIPS mode
Boot with the Cisco IOS Release 15.2(1)E image.
The boot loader is
not updated.
The image
signature is not verified
The switch works
normally.
Configure an existing FIPS complaint switch running Cisco IOS
Release 15.2(1)E to work in a non-FIPS mode.
Configure the
no fips authorization- keyauthorization-key global configuration command.
Reload the switch
for the configuration to take effect. By default, the switch automatically
boots up; however, if you have configured it to boot up manually, you have to
initiate the reboot.
The boot loader is
not updated.
The switch works
normally and the FIPS commands are no longer available.
The following
message appears in the boot sequence: “Image passed digital signature
verification”.
Note
If you upload a corrupt or unsigned image, the following
message appears during boot up: “WARNING: Unable to determine image
authentication. Image is either unsigned or is signed but corrupted.”
Downgrade from a Cisco IOS Release 15.2(1)E image in FIPS mode
to an older release.
Configure the no
fips authorization- key authorization-key global configuration command
Reload the switch
for the configuration to take effect. By default, the switch automatically
boots up; however, if you have configured it to boot up manually, you have to
initiate reboot.
Upload and boot
the older image.
The boot loader is
not downgraded
The switch work
normally and the FIPS commands are no longer available.
The following
message appears in the boot sequence: “WARNING: Unable to determine image
authentication. Image is either unsigned or is signed but corrupted.”
Monitoring Switch Setup Configuration
Example: Verifying the Switch Running Configuration
Switch# show running-config
Building configuration...
Current configuration: 1363 bytes
!
version 12.4
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Stack1
!
enable secret 5 $1$ej9.$DMUvAUnZOAmvmgqBEzIxE0
!
.
<output truncated>
.
interface gigabitethernet6/0/2
mvr type source
<output truncated>
...!
interface VLAN1
ip address 172.20.137.50 255.255.255.0
no ip directed-broadcast
!
ip default-gateway 172.20.137.1 !
!
snmp-server community private RW
snmp-server community public RO
snmp-server community private@es0 RW
snmp-server community public@es0 RO
snmp-server chassis-id 0x12
!
end
Configuration Examples for Performing Switch Setup
Example: Configuring a Switch as a DHCP Server
Switch# configure terminalSwitch(config)# ip dhcp poolpool1Switch(dhcp-config)# network10.10.10.0 255.255.255.0Switch(dhcp-config)# bootconfig-boot.textSwitch(dhcp-config)# default-router 10.10.10.1Switch(dhcp-config)# option 150 10.10.10.1Switch(dhcp-config)# exitSwitch(config)# tftp-server flash:config-boot.textSwitch(config)# interface gigabitethernet1/0/4 Switch(config-if)# no switchportSwitch(config-if)# ip address 10.10.10.1 255.255.255.0Switch(config-if)# end
Example: Configuring DHCP Auto-Image Update
Example: Configuring a Switch to Download Configurations from a DHCP Server
This example uses a Layer 3 SVI interface on VLAN 99 to enable DHCP-based autoconfiguration with a saved configuration:
Switch# configure terminalSwitch(config)# boot host dhcpSwitch(config)# boot host retry timeout 300Switch(config)# banner config-save ^C Caution - Saving Configuration File to NVRAM May Cause You to No longer Automatically Download Configuration Files at Reboot^CSwitch(config)# vlan 99Switch(config-vlan)# interface vlan 99Switch(config-if)# no shutdownSwitch(config-if)# endSwitch# show boot
BOOT path-list:
Config file: flash:/config.text
Private Config file: flash:/private-config.text
Enable Break: no
Manual Boot: no
HELPER path-list:
NVRAM/Config file
buffer size: 32768
Timeout for Config
Download: 300 seconds
Config Download
via DHCP: enabled (next boot: enabled)
Switch#
Examples: Scheduling Software Image Reload
This example shows how to reload the software on the switch on the current day at 7:30 p.m:
Switch# reload at 19:30
Reload scheduled for 19:30:00 UTC Wed Jun 5 2013 (in 2 hours and 25 minutes)
Proceed with reload? [confirm]
This example shows how to reload the software on the switch at a future time:
Switch# reload at 02:00 jun 20
Reload scheduled for 02:00:00 UTC Thu Jun 20 2013 (in 344 hours and 53 minutes)
Proceed with reload? [confirm]