3-6
Software Configuration Guide—Release 12.2(25)SG
OL-7659-03
Chapter3 Configuring the Switch for the First Time
Configuring DHCP-Based Autoconfiguration
Figure3-2 Relay Device Used in Autoconfiguration
Obtaining 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 are 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 th e configuration
filename from either the DHCP server or the DHCP server feature run ning on your switch. 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, completes its boot-up proc ess.
•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 either the
DHCP server or the DHCP server feature running on your switch. The swi tch sends a broadcast
message to a TFTP server to retrieve the named configuration file from the base directory of the
server, and upon receipt, 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 either the DHCP
server or the DHCP server feature running on your switch. 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 host names-to-IP-address mapping for the switch. The
switch fills its host table with the information in the file and obtains its host name. If the host name
is not found in the file, the switch uses the host name in the DHCP reply. If the host name is not
specified in the DHCP reply, the switch uses the default Switch as its host name.
After obtaining its host name from the default configuration file or the DHCP reply, the switch reads
the configuration file that has the same name as its host name (hostname-confg or hostname.cfg,
depending on whether or not the network-confg file or the cisconet.cfg file was read earlier) from
the TFTP server. If the cisconet.cfg file is read, the filename of the host is truncated to eight
characters.
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