DELL N3000 User Manual

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.