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Cisco Small Business SG200 Series 8-port Smart Switch 63
3
Overview
During startup, the switch attempts communication with a DCHP server to obtain
its IP address and other information. If Auto Configuration is enabled, the switch
may also download a startup configuration file, depending on the TFTP server and
startup configuration file name it receives from the DHCP server. Auto
Configuration is enabled by default.
DHCP Auto Configuration initiates when the switch is rebooted with Auto
Configuration enabled, and any of the following conditions occur:
1. Information on the TFTP server and Startup Configuration is received from the
DHCP server, and Auto Configuration has not previously downloaded the
configuration file.
2. Information on the TFTP server and Startup Configuration is received from the
DHCP server, and the configuration file name differs from the file name
advertised in a previous DHCP message.
3. The Startup Configuration file is not present and no information on the TFTP
server or Startup Configuration is received from the DHCP server.
When conditions 1 and 2 occur, the switch saves the file to flash memory. Upon
subsequent startups, it compares the stored file name to the name specified in
option 66/67 in the current DHCP message. If they differ, the new file is
downloaded and written to flash memory.
NOTE When the system boots up for the first time, the switch does not have a specific
name for the configuration file received from the DHCP server, as it has not
downloaded a Startup Configuration file yet. If these options are received in the
DHCP message, then that file name is saved and the download process begins.
When option 3 occurs, the switch looks for the TFTP server and Startup
Configuration file as described in Default Network Configuration File.
DHCP Server Message Details
Any of the following fields might be returned by a BOOTP or DHCP server and
processed by the switch:
• The name of the configuration file (boot file or option 67) to be downloaded
from the TFTP server.
• The identification of the TFTP server from which to obtain the boot file.
The TFTP server IP address can be deduced from the multiple sources in a
DHCP reply. The switch makes its selection based on the following criteria,
from the highest priority to the lowest: