Using automatic configuration update with DHCP Option 66
HPE switches are initially booted up with the factory-shipped configuration file. The automatic configuration update provides a way to automatically download a different configuration file from a TFTP server using DHCP Option 66.
Prerequisites
To use automatic configuration update with DHCP Option 66, you must do the following:
Enable one or more DHCP servers with Option 66.
Insure that one or more TFTP servers have the desired configuration file.
Insure that the configuration files to be updated were generated on the switch.
Enable the configuration file to update with Option 66, as described in Enabling and disabling the configuration file update using Option 66.
Enabling and disabling the configuration file update using Option 66
Use the
dhcp config-file-updatecommand to enable the configuration update using Option 66.Use the
no dhcp config-file-updatecommand to disable the configuration update using Option 66.
The configuration file update using Option 66 is enabled by default.
Possible scenarios for updating the configuration file
The following table shows various network configurations and how Option 66 is handled.
| Scenario | Behavior |
|---|---|
| Single Server serving Multiple VLANs |
|
| Multiple Servers serving a Single VLAN |
|
| Multiple Servers serving Multiple VLANs |
|
| Multi-homed Server serving Multiple VLANs |
|
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".