Administrator Guide

DHCP and USB Auto-Configuration 553
Obtaining the Configuration File
If the DHCP OFFER identifies a specific configuration file, either as option
67 or in the file field of the DHCP header, the switch attempts to download a
network configuration file.
The TFTP client makes three unicast requests if the TFTP server is
reachable. A TFTP server is not reachable if it does not respond to ARP, if its
DNS name (DHCP option 66) does not resolve, or if the TFTP server does
not respond to TFTP Read Requests. If the unicast attempts fail, or if the
DHCP OFFER did not specify a TFTP server address, the auto-configuration
download fails.
If the DHCP server does not specify a configuration file or download of the
specific configuration file fails, the Auto Configuration process makes three
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 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
If a hostname has been identified, the switch issues up to three TFTP
requests for a file named hostname.cfg , where hostname is the first
thirty-two characters of the switch's hostname.
NOTE: The configuration file is required to have a file name that matches the
following pattern: "*.cfg"