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Protocol Operations - Technical Summary

This document provides a technical summary of DHCPv6 protocol operations as specified in sections 17-22 of RFC 3315.

17. DHCP Server Solicitation​

Purpose: Client discovers servers that can assign addresses

Client Behavior:

  • Creates IA and assigns IAID
  • Sends Solicit message
  • May include Rapid Commit option
  • Collects Advertise messages for first RT
  • Selects server based on preference value

Server Behavior:

  • Receives Solicit message
  • Checks administrative policy
  • Sends Advertise or Reply (with Rapid Commit)
  • May include Preference option

18. DHCP Client-Initiated Configuration Exchange​

Message Types: Request, Renew, Rebind, Release, Decline, Confirm, Information-request

Key Operations:

  • Request: Populates IA with addresses
  • Confirm: Validates addresses after link change
  • Renew: Extends address lifetimes (at T1)
  • Rebind: Extends lifetimes from any server (at T2)
  • Release: Returns addresses to server
  • Decline: Reports duplicate addresses
  • Information-request: Requests configuration without requesting addresses

19. DHCP Server-Initiated Configuration Exchange​

Reconfigure Message:

  • Server initiates client reconfiguration
  • Client must accept Reconfigure messages (Reconfigure Accept option)
  • Triggers client's Renew or Information-request

20. Relay Agent Behavior​

Functions:

  • Relays messages between clients and servers on different links
  • Adds Interface-Id option
  • Increments hop count
  • Encapsulates messages in Relay-forward/Relay-reply

21. Authentication of DHCP Messages​

Protocols:

  • Delayed Authentication Protocol
  • Reconfigure Key Authentication Protocol

Security:

  • IPsec recommended for server-relay communication
  • Authentication option for client-server messages

22. DHCP Options​

RFC 3315 defines 20 standard DHCPv6 options:

  1. OPTION_CLIENTID (1) - Client Identifier
  2. OPTION_SERVERID (2) - Server Identifier
  3. OPTION_IA_NA (3) - Identity Association for Non-temporary Addresses
  4. OPTION_IA_TA (4) - Identity Association for Temporary Addresses
  5. OPTION_IAADDR (5) - IA Address
  6. OPTION_ORO (6) - Option Request
  7. OPTION_PREFERENCE (7) - Preference
  8. OPTION_ELAPSED_TIME (8) - Elapsed Time
  9. OPTION_RELAY_MSG (9) - Relay Message
  10. OPTION_AUTH (11) - Authentication
  11. OPTION_UNICAST (12) - Server Unicast
  12. OPTION_STATUS_CODE (13) - Status Code
  13. OPTION_RAPID_COMMIT (14) - Rapid Commit
  14. OPTION_USER_CLASS (15) - User Class
  15. OPTION_VENDOR_CLASS (16) - Vendor Class
  16. OPTION_VENDOR_OPTS (17) - Vendor-specific Information
  17. OPTION_INTERFACE_ID (18) - Interface ID
  18. OPTION_RECONF_MSG (19) - Reconfigure Message
  19. OPTION_RECONF_ACCEPT (20) - Reconfigure Accept

Option Format​

All options use the following format:

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          option-code          |           option-len          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                          option-data                          |
|                      (option-len octets)                      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Reference​

For complete protocol specification, refer to the official RFC 3315:

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