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Catalyst 2950 Desktop Switch Software Configuration Guide
78-14982-01
Chapter 4 Assigning the Swi tch IP Address and De fault Gate way Assigning Switch Information
Figure 4-2 Relay Device Used in Autoconfiguration

Obtaining Configuration Files

Depending on the availability of the I P address and the configuration filename in the DHCP reserved
lease, the switch obtains its configuration information in these way s:
•The IP ad dr es s an d th e co n figuration filename is r eser ved for the switc h an d provided in the DHCP
reply (on e-file read method ).
The sw itch re ceives its IP addr ess , subnet mask, TFTP ser ver add ress, an d the co nfigurati on
filename from the DHCP server. The switch sends a unicast message to the TFTP server to retrieve
the name d configurat ion file fr om the base d irect or y of the se rver, and u pon r ece ipt, c om ple tes its
boot-up proc ess .
•The IP address and the config uration filename is reserved for the switch, but the TFTP server
address is not provided in the DHCP reply (one-file read method).
The switc h receives its IP addres s, subnet mask, and the configuration filenam e from the DHCP
server. The switch sends a broadcast message to a TFTP server to retrieve the named configuration
file from th e base di rec tory of the s erver, and upon re ceip t, com plete s it s boot- up proce ss.
•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 receiv es 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 retriev e the network-confg or cisconet.cfg
default conf iguration file. (If the network-confg f ile cannot be read, the switch reads the cisconet.cfg
fil e.)
The default configuration file conta ins the ho st names-to -IP-addre ss mappin g for the switch . The
switch fills its host table with th e inform ati on in the file and obtains its host name. If the host name
is not found i n t he file, the swit ch u ses t he h ost n am e i n th e DHCP repl y. If the host na me is n ot
specified in the DHCP reply, th e switch uses the default Switch as its host name.
After obtaining its host name fr om the default co nfiguratio n file or the DHCP reply , the switch reads
the configuration file that has the same name as its host name (hostname-c onf g or hostname.cfg,
depending on whether network-confg or cisconet.cf g was read earlier) from the TF TP server. If the
cisconet.cf g file is read, the filename of the host is truncated to eight characters.
If the swi tc h ca nno t re ad t he ne twork- confg , cisc on et. cfg, or the h ostna me file, it read s the
router-con fg file. If the swi tch canno t read th e router-con fg file, it read s the ciscor tr.cf g file.
Switch
(DHCP client) Cisco router
(Relay)
49068
DHCP server TFTP server DNS server
20.0.0.2 20.0.0.3
20.0.0.1
10.0.0.2
10.0.0.1
20.0.0.4