Dell POWEREDGE M1000E - Manual (Page 390)

390 Auto Image and Configuration Update
The TFTP client makes three unicast requests. If the unicast attempts fail, or
if the DHCP OFFER did not specify a TFTP server address, the TFTP client
makes three broadcast requests.
If the DHCP server does not specify a configuration file or download of the
configuration file fails, the Auto Configuration process attempts to download
a configuration file with the name dell-net.cfg. The switch unicasts or
broadcasts TFTP requests for a network configuration file in the same
manner as it attempts to download a host-specific configuration file.
The default network configuration file consists of a set of IP address-to-
hostname mappings, using the command ip host hostname address . The
switch finds its own IP address, as learned from the DHCP server, in the
configuration file and extracts its hostname from the matching command. If
the default network configuration file does not contain the switch's IP
address, the switch attempts a reverse DNS lookup to resolve its hostname.
A sample dell-net.cfg file follows:
config
...
ip host switch1 192.168.1.10
ip host switch2 192.168.1.11
... <other hostname definitions>
exit
Once a hostname has been determined, the switch issues a TFTP request for
a file named hostname.cfg , where hostname is the first thirty-two
characters of the switch's hostname.
If the switch is unable to map its IP address to a hostname, Auto
Configuration sends TFTP requests for the default configuration file
host.cfg.
NOTE: The configuration file is required to have a file type of *.cfg.