Typical Autoinstallation Process on a New Services Router

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

1. The new Services Router 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 router 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 router if the configuration server is on a different LAN segment from the new router.
2. After the new Services Router acquires an IP address, the autoinstallation process on the router 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 router uses that filename in the TFTP server request. (In the filename, hostname is the hostname of the new router.) The autoinstallation process on the new router makes three unicast TFTP requests for hostname.conf. If these attempts fail, the router broadcasts three requests to any available TFTP server for the file.
   2. If the new router cannot locate hostname.conf, the autoinstallation process unicasts or broadcasts TFTP requests for a default router 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 Services Router, the autoinstallation process sends out a DNS request and attempts to resolve the new router's IP address to a hostname.
   4. If the new Services Router can determine its hostname, it sends a TFTP request for the hostname.conf file.
   5. If the new Services Router 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 Services Router locates a configuration file on a TFTP server, autoinstallation downloads the file, installs the file on the router, and commits the configuration.