Switch Memory and Configuration

 

Automatic Configuration Update with DHCP Option 66

 

 

Scenario

Behavior

 

 

Multiple Servers serving Multiple VLANs

• Each DHSP-enabled VLAN interface initiates DHCPDISCOVER and

 

receives one or more DHCPOFFER messages.

 

• Each interface accepts the best offer.

 

• Option 66 is processed only for the interface belonging to the primary

 

VLAN.

Multi-homed Server serving Multiple VLANs • The switch perceives the multi-homed server as multiple separate servers.

Each DHCP-enabled VLAN interface initiates DHCPDISCOVER and receives one DHCPOFFER message.

Each interface accepts the offer.

Option 66 is processed only for the interface belonging to the primary VLAN.

Operating Notes

Replacing the Existing Configuration File: After the DHCP client down­ loads 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 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”

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