DHCPv6 Server Configuration

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• IPv6 SLAAC process can locate the default gateway and generate a host address with network prefix automatically
• thus, DHCPv6 is often just used to provide additional option settings
  • rather than leases for host IP addresses
• process of DHCP server discovery and address leasing is fundamentally the same
  • but format of messages is different
  • as IPV6 does not support broadcast, clients use the multicast address ff02::1:2 to discover a DHCP server
  • DHCPv6 uses ports 546 (clients) and 547 (servers)

Stateless Mode

• in stateless mode, client obtains a network prefix from a router advertisement and uses it with the appropriate interface ID
  • router can also set a combo of flags to tell the client that a DHCP server is available
• if so configured, client solicits a DHCPv6 server using multicast address and request additional configuration information

Stateful Mode

• stateful mode means that a host can also obtain a routable IP address form a DHCPv6 scope
• in both modes, DHCPv6 server can supply options information
  • e.g., DNS server addresses, DNS suffix/domain lists, time servers

• to configure scope, need to define:
  • the network prefix
  • then any IP addresses that are to be excluded form being offered
• host must still listen for a router advertisement to obtain the network prefix and configure a default gateway
• no mechanism in DHCPv6 for setting the default route

Info

It is possible to configure a static reservation in DHCPv6

• doesn’t use a MAC address
• instead, each system generates a host DHCP Unique Identifier (DUID) plus an Identity Association Identifier (IAID) for each interface