Typical Autoinstallation Process on a New Device

When a device is powered on for the first time, it performs the following autoinstallation tasks:

1. The new device sends out DHCP, BOOTP, RARP, or SLARP requests on each connected interface simultaneously to obtain an IP address.

   If a DHCP server responds, it provides the device with some or all of the following information:

   • An IP address and subnet mask for the autoinstallation interface.
   • The location of the TFTP (typically), Hypertext Transfer Protocol (HTTP), or FTP server on which the configuration file is stored.
   • The name of the configuration file to be requested from the TFTP server.
   • The IP address or hostname of the TFTP server.

     If the DHCP server provides only the hostname, a DNS server must be available on the network to resolve the name to an IP address.

   • The IP address of an intermediate device if the configuration server is on a different LAN segment from the new device.
2. After the new device acquires an IP address, the autoinstallation process on the device attempts to download a configuration file in the following ways:
   1. If the DHCP server specifies the host-specific configuration file (boot file) hostname.conf, the device uses that filename in the TFTP server request. (In the filename, hostname is the hostname of the new device.) The autoinstallation process on the new device makes three unicast TFTP requests for hostname.conf. If these attempts fail, the device broadcasts three requests to any available TFTP server for the file.
   2. If the new device cannot locate hostname.conf, the autoinstallation process unicasts or broadcasts TFTP requests for a default device configuration file called network.conf, which contains hostname-to-IP address mapping information, to attempt to find its hostname.
   3. If network.conf contains no hostname entry for the new device, the autoinstallation process sends out a DNS request and attempts to resolve the new device's IP address to a hostname.
   4. If the new device can determine its hostname, it sends a TFTP request for the hostname.conf file.
   5. If the new device is unable to map its IP address to a hostname, it sends TFTP requests for the default configuration file router.conf.
3. After the new device locates a configuration file on a TFTP server, autoinstallation downloads the file, installs the file on the device, and commits the configuration.