6-5
Catalyst 2950 Desktop Switch Software Configuration Guide
78-11380-03
Chapter 6 Configuring the System
Changing IP Information
Note If the configuration file on the switch does not contain the IP address, the switch obtains its address,
mask, gateway IP address, and host name from DHCP. If the service config global configuration
command is specified in the configuration file, the switch receives the configuration file through TFTP
requests. If both the service config global configuration command and the IP address are in the
configuration file, DHCP is not used, and the switch obtains the default configuration file by
broadcasting TFTP requests.
The DHCP server can be on the same or a different LAN as the switch. If it is on a different LAN, the
switch must be able to access it through a relay device.
For more information, see the “Configuring the Relay Device” section on page 6-6. You must also set
the TFTP server with the switch configuration files; for more information, see the next section.
For CLI procedures, refer to the Cisco IOS Release 12.1 documentation on Cisco.com for additional
information and CLI procedures.
Configuring the TFTP Server
The TFTP server must contain one or more configuration files in its base directory. The files can include
these:
• 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.)
You must specify the TFTP server name in the DHCP-server lease database. You must also specify the
TFTP server name-to-IP-address mapping in the DNS-server database.
The TFTP server can be on the same or on a different LAN as the switch. If it is on a different LAN, the
switch must be able to access it through a relay device or a router. For more information, see the
“Configuring the Relay Device” section on page 6-6.
If the configuration filename is provided in the DHCP server reply, the configuration files for a switch
can be spread over multiple TFTP servers. However, if the configuration filename is not provided, the
configuration files must reside on a single TFTP server.
For CLI procedures, refer to the Cisco IOS Release 12.1 documentation on Cisco.com for additional
information and CLI procedures.
Configuring the Domain Name and the DNS
Each unique IP address can have a host name associated with it. The IOS software maintains a cache of
host name-to-address mappings for use by the EXEC mode connect, telnet,andping commands, and
related Telnet-support operations. This cache speeds the process of converting names to addresses.
IP defines a hierarchical naming scheme that allows a device to be identified by its location or domain.
Domain names use periods (.) as the delimiting characters. For example, Cisco Systems is a commercial
organization that IP identifies by a com domain name, so its domain name is cisco.com. A specific device
in this domain, the File Transfer Protocol (FTP) system for example, is identified as ftp.cisco.com.
To keep track of domain names, IP has defined the concept of a Domain Name Server (DNS), which
holds a cache (or database) of names mapped to IP addresses. To map domain names to IP addresses,
you must first identify the host names and then specify a name server and enable the DNS, the Internet’s
global naming scheme that uniquely identifies network devices.
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