Operating notes about automatic configuration

Replacing the existing configuration file: After the switch has completed the DHCP transaction on the Primary VLAN, the two options will cause the switch to download the configuration file from the TFTP server. After the DHCP client downloads the configuration file, the switch compares the contents of that file with the existing configuration file. If the content is different, the new configuration file replaces the existing file and the switch reboots.

Option 66 and the IP address of a TFTP server: Option 66 includes the IP address of the TFTP server from which the configuration file is downloaded.

Option 67 and the configuration file name: Option 67 includes the name of the configuration file. If the DHCPACK contains this option, it overrides the default name for the configuration file (switch.cfg)

Global DHCP parameters: Global parameters are processed only if received on the primary VLAN.

Best Offer: The "Best Offer" is the best DHCP or BootP offer sent by the DHCP server in response to the DHCPREQUEST sent by the switch. The criteria for selecting the "Best Offer" are:

  • DHCP is preferred over BootP

  • If two BootP offers are received, the first one is selected

  • For two DHCP offers:
    • The offer from an authoritative server is selected

    • If there is no authoritative server, the offer with the longest lease is selected

Log messages: The file transfer is implemented by the existing TFTP module. The system logs the following message if an incorrect IP address is received for Option 66: "Invalid IP address <ip-address> received for DHCP Option 66".