DHCPv4 Server NAK Support

The Dynamic Host Configuration Protocol version 4 (DHCPv4) server on RUCKUS ICX devices sends a Negative Acknowledgment (DHCPNAK) when a client requests an invalid or unavailable leased IP address, prompting immediate rediscovery.

Feature Overview

In a standard DHCP exchange, when a client moves from one network segment to another, it may attempt to request its previously assigned IP address using DHCP Option 50 (Requested IP Address). If the ICX DHCP server determines that the requested IP address is not valid for the client's current subnet or is no longer available, it sends a DHCPNAK message. The client then restarts the DHCP discovery process (DHCPDISCOVER) to obtain a valid IP address.

Requirements

This feature has no special hardware or software requirements for feature enablement or usage.

Considerations

Consider the following when configuring and using this feature:

  • When a DHCP client moves to a different network and requests its previously assigned address (DHCP Option 50), the DHCP server sends a DHCPNAK message if the address is invalid for the new network segment.
  • After receiving the DHCPNAK message, the client restarts the DHCP address allocation process.
  • The DHCP server does not send a DHCPNAK message in response to a DHCP lease renewal request.

Limitations

Note the following limitations regarding this feature:

  • The DHCP server does not send a DHCPNAK message when the requested address does not belong to any address pool configured on the DHCP server.
  • The DHCP server does not send a DHCPNAK message when the requested address is an excluded address.
  • The DHCP server does not send a DHCPNAK message when the requested address belonged to an address pool that has been deleted.

Best Practices

This feature has no special recommendations for feature enablement or usage.

Prerequisites

  • The DHCPv4 server must be enabled.
  • At least one DHCP address pool must be configured.
Parent topic: DHCP Servers