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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
OL-10101-02
Chapter 4 Assigning the Switch IP Address and Default Gateway
Assigning Switch Information
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)
• Host name (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 subnet mask are not in the
reply, the switch is not configured. If the router IP address or 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.
Configuring 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. For more information, see the “Configuring the Relay Device” section on page 4-7. The
preferred solution is to configure the DHCP server with all the required information.