DHCPv6

Fundamentals

  • DHCPv6 clients listen on port 546, servers and relays listen on port 547
  • DHCPv6 clients and servers (relays) communicate via link-local multicast addresses
    • All_DHCP_Relay_Agents_and_Servers and All_DHCP_Servers multicast addresses are used

All_DHCP_Relay_Agents_and_Servers : FF02:0:0:0:0:0:1:2(All-dhcp-agents)
IPv6 multicast MAC addresses : 33:33:00:01:00:02

DHCPv6 to DHCPv4 Message Comparison

-DHCPv6 Message Type                  -DHCPv4 Message Type 
SOLICIT (1)                           DHCPDISCOVER 
ADVERTISE (2)                         DHCPOFFER 
REQUEST (3), RENEW (5), REBIND (6)    DHCPREQUEST 
REPLY (7)                             DHCPACK / DHCPNAK 
RELEASE (8)                           DHCPRELEASE 
INFORMATION-REQUEST (11)              DHCPINFORM 
DECLINE (9)                           DHCPDECLINE 
CONFIRM (4)                           none 
RECONFIGURE (10)                      DHCPFORCERENEW 
RELAY-FORW (12)                       none
RELAY-REPLY (13)                      none

Client Identification

  • DHCPv6 DUID (DHCP Unique Identifier) as defined in RFC3315
    • Link-layer address plus time – generated and stored at startup
    • Link-layer – generally used if network interface is permanent or unchangeable
    • Vendor assigned unique identifier based on enterprise identifier

DHCPv6 Type

  • Stateless DHCPv6
    • Two message exchange (INFORMATION-REQUEST, REPLY) between a DHCPv6 client and server
          Server  Client
             | <---- |  INFORMATION-REQUEST
             | ----> |  REPLY
             V       V
      
  • Stateful DHCPv6
    • Four message exchange (SOLICIT, ADVERTISE, REQUEST, REPLY)
    • Rapid Commit may be employed which uses only two message (SOLICIT, REPLY)
          Server  Client
             | <---- |  SOLICIT (Rapid Commit)
             | ----> |  ADVERTISE
             | <---- |  REQUEST
             | ----> |  REPLY (Rapid Commit)
             V       V
      
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