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Cisco Wireless LAN Controller Configuration Guide
OL-17037-01
Chapter 4 Configuring Controller SettingsWireless Device Access
Using the AutoInstall Feature for Controllers Without a Configuration
Obtaining an IP Address Through DHCP and Downloading a Configuration File
from a TFTP Server
AutoInstall uses the following interfaces:
•
4400 series controllers
–
eth0—Service port (untagged)
–
dtl0—Gigabit port 1 through the NPU (untagged)
•
2100 series controllers
–
dtl0—FastEthernet port 1 (untagged)
AutoInstall attempts to obtain an IP address from the DHCP server until the DHCP process is successful
or until you abort the AutoInstall process. The first interface to successfully obtain an IP address from
the DHCP server registers with the AutoInstall task. The registration of this interface causes AutoInstall
to begin the process of obtaining TFTP server information and downloading the configuration file.
Following the acquisition of the DHCP IP address for an interface, AutoInstall begins a short sequence
of events to determine the host name of the controller and the IP address of the TFTP server. Each phase
of this sequence gives preference to explicitly configured information over default or implied
information and to explicit host names over explicit IP addresses.
The process is as follows:
•
If at least one Domain Name System (DNS) server IP address is learned through DHCP, AutoInstall
creates a /etc/resolv.conf file. This file includes the domain name and the list of DNS servers that
have been received. The Domain Name Server option provides the list of DNS servers, and the
Domain Name option provides the domain name.
•
If the domain servers are not on the same subnet as the controller, static route entries are installed
for each domain server. These static routes point to the gateway that is learned through the DHCP
Router option.
•
The host name of the controller is determined in this order by one of the following:
–
If the DHCP Host Name option was received, this information (truncated at the first period [.])
is used as the host name for the controller.
–
A reverse DNS lookup is performed on the controller IP address. If DNS returns a host name,
this name (truncated at the first period [.]) is used as the host name for the controller.
•
The IP address of the TFTP server is determined in this order by one of the following:
–
If AutoInstall received the DHCP TFTP Server Name option, AutoInstall performs a DNS
lookup on this server name. If the DNS lookup is successful, the returned IP address is used as
the IP address of the TFTP server.
–
If the DHCP Server Host Name (sname) field is valid, AutoInstall performs a DNS lookup on
this sname. If the DNS lookup is successful, the IP address that is returned is used as the IP
address of the TFTP server.
–
If AutoInstall received the DHCP TFTP Server Address option, this address is used as the IP
address of the TFTP server.
–
AutoInstall performs a DNS lookup on the default TFTP server name (cisco-wlc-tftp). If the
DNS lookup is successful, the IP address that is received is used as the IP address of the TFTP
server.
