IPv6 and DHCPv6
In my endeavors to pass certification tests I learn all kinds of stuff that I think is cool to pass on. I am learning about IPv6 and some of the in and outs of different services for it. This post will cover some things I am learning about IPV6 and DHCPv6. DHCP for IPv6 is quite different than DHCP for IPv4. The first thing with IPv6 and DHCP is that IPv6, auto configuration of hosts is possible because subnet and default gateway information can be delivered by routers, while host addresses are automatically generated or derived from the MAC address. There are two ways to do this:
The first is called stateless. This is used to deliver DNS server information and other configuration information that can’t be delivered by the router. This is done by setting the M Flag to zero and the O flag to one.
The second is called stateful. This is to deliver all configuration information, including the prefix and interface ID by setting the M and O flags to one.
The M and O flags indicate whether Host Configuration/Information Configuration Behaviors are available, but typically they themselves should not be used as triggers to invoke DHCPv6 services. However, these flags in conjunction with the policy configured may trigger DHCPv6 services for automatic configuration of the IPv6 address and the other information.
Also if stateful DHCPv6 is used the server follows the following message exchange between the client and the server.
- First the client sends a solicit packet to solicit information from a DHCP server.
- Then the DHCP server will send an advertise packet back to the client to indicate that it has the address information.
- Then the client will send back a request packet to officially request the address assignment.
- The DHCP server will the send a reply packet to the client acknowledging the client’s addressing assignment.
This is a little different than the DORA process that DHCP for IPv4 uses, but they both accomplish the same mission. Also the overall configuration fo the DHCP server is pretty similar with configuration of the scope, exclusions, reservations, and scope options. IPv6 is the wave of the future and it will help if you learn it now, in the next 10 years we may see the discontinued use of IPv4. Good luck and I hope this helps shed some light on the subject.