Module 8: SLAAC and DHCPv6

GUA

Global Unicast Address

Stateless

No device is tracking the assignment of IPv6 Addresses

Stateful

A DHCPv6 Server is managing the assignment of IPv6 Addresses

SLAAC Only (Stateless)

Router sends Router Advertisment (RA) messages providing all IPv6 addressing info

Hosts use the RA info for all their adressing, incl. their own GUA

SLAAC with DHCP Server (Stateless DHCPv6)

Router send RA messages to hosts with configuration information, inform them to contact stateless DHCPv6 Server for additional configs

Hosts use RA info to create own GUA and get additional info from server

DHCPv6 Server (Stateful DHCPv6)

Router send RA messages to inform hosts to contact a DHCPv6 server or router for all config information (except default gateway → obtained from RA messages)

A flag (RA)

Adress Autoconfiguration = use SLAAC to create GUA

O flag (RA)

Other Configuration = additional information from a stateless DHCPv6 server

M flag (RA)

Managed Address Configuration = use statefulss DHCPv6 server

ICMPv6 RS messages

Router sends RA messages every 200 seconds OR when it receives a RS from a host

Host wants to receive IPV6 addressing information → send RS message to all-router multicast address ff02::2

Generate Interface ID

Subnet information from RA but Interface ID

Randomly by OS from client

EUI-64 using the mac address + fffe in middle of address

Duplicate Address Detection (DAD)

NS (Neighbor Solicitation) with solicited-node multicast address with last 24 bits of IPv6 address of host

If no devices reply with a NS, the address is available

Stateful DHCPv6

1. The host sends an RS message. 

2. The router responds with an RA message. 

3. The host sends a DHCPv6 SOLICIT message. 

4. The DHCPv6 server responds with an ADVERTISE message.  5. The host responds to the DHCPv6 server. 

6. The DHCPv6 server sends a REPLY message.