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Catalyst 3550 Multilayer Switch Software Configuration Guide
78-11194-03
Chapter4 Assigning the Switch IP Address and Default Gateway Assigning Switch Information
Figure4-2 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 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 t he se rv er, and upon re cei pt, comp let es i ts
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 met hod ).
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, comp let es i ts b oot- up pro cess.
•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 r ead, the switch reads the cisconet.cfg
file.)
The default configuration file contains the host names-to-I P-addr ess mapp in g for t he sw itc h. Th e
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 D HC P re ply. If the host n ame is no t
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 re ply, the switch reads
the configuration file that has the same name as its host name (hostname-confg or hostname.cfg,
depending on whether network-confg or cisconet.cfg was read ea rlier) from the TFTP server. If the
cisconet.cfg file is read, the filename of the host is truncat ed t o eight ch arac ters .
If the switch cannot read the network-confg, cisconet.cfg, or the ho stna me f ile, i t rea ds the
router-confg file. If the switch cannot read the router-confg file, it reads the ciscortr.cfg 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