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

  • Each DHCP-enabled VLAN interface initiates DHCPDISCOVER message, receives DHCPOFFER from the server, and send DHCPREQUEST to obtain the offered parameters.

  • If multiple interfaces send DHCPREQUESTs, it is possible that more than one DHCPACK is returned with a valid Option 66.

  • Evaluating and updating the configuration file occurs only on the primary VLAN.

  • Option 66 is ignored by any interfaces not belonging to the primary VLAN.

Multiple Servers serving a Single VLAN

  • Each DHCP-enabled VLAN interface initiates one 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.

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.