DHCP promotion

DHCP promotion allows data-triggered subscriber hosts to become DHCP hosts.

After a data-triggered host is created, DHCP packets sent by the client starts the DHCP promotion process as follows:

  1. A DHCP Request/Renew/Rebind message comes from the data-triggered host.

  2. Authentication using LUDB and RADIUS is performed. A RADIUS Access-Request message is sent if the authentication policy has re-authentication enabled. DHCP processing is done without authentication if re-authentication is not configured.

  3. An Access-Accept message that contains ESM attributes is sent back from the AAA server. If an Access-Reject message is received, the data-triggered host is deleted.

  4. A DHCP packet is relayed to the DHCP server.

  5. A DHCP server replies with a DHCP Ack/Relay-Reply or Nak message.

  6. When an Ack/Relay-Reply message is received, a lease state is created, and the data-triggered host is promoted to the DHCP host.

  7. If the DHCP server replies with Nak or with IP address information different from the existing data-triggered host, DHCP promotion fails and the data-triggered host is deleted.

  8. With DHCP proxy, if the LUDB or AAA server returns IP information different from the data-triggered host, then DHCP promotion fails and the data-triggered host is deleted.

  9. An interim accounting message is generated based on the configuration of the radius-accounting-policy command, as follows:

    1. queue-instance-accounting: interim-update with Alc-Acct-Triggered-Reason = Promotion of a Data-triggered host.

    2. session-accounting: interim-update with Alc-Acct-Triggered-Reason = Promotion of a Data-triggered host, if host-update is configured.

    3. host-accounting: interim-update with Alc-Acct-Triggered-Reason = Promotion of a Data-triggered host

Data-triggered hosts can be promoted to DHCP proxy hosts by default. To promote data-triggered hosts using DHCP relay to an internal or external DHCP server, the Alc-Force-DHCP-Relay VSA is included in Access-Accept messages to authenticate data-triggered hosts.

Figure: DHCP promotion with DHCP relay shows DHCP promotion with DHCP relay.

Note: DHCP relay promotion is only supported when using RADIUS. LUDB and NASreq is not supported.
Figure: DHCP promotion with DHCP relay
Parent topic: Data-triggered subscriber management