In Windows Server 2008 (WS08), Microsoft has introduced DHCPv6 functionality to the DHCP server.

In Windows Server 2008 (previously known as "Longhorn" Server) Beta 2, we released the DHCPv6 Stateless Server functionality. In Beta 3, we are introducing the DHCPv6 Stateful Server functionality. As I explained in my previous post DHCPv6 behaviour in Windows Vista, in the DHCPv6 stateless mode clients use DHCPv6 only to obtain network configuration parameters other than the IPv6 address. In this scenario, clients configure an IPv6 address through a non-DHCPv6 based mechanism (possibly through IPv6 address auto-configuration based on the IPv6 prefixes included in Router Advertisements, or through static configuration.) In the DHCPv6 stateful mode, clients acquire both the IPv6 address as well as other network configuration parameters through DHCPv6.

In WS08 Beta 3, our Beta and TAP customers will have access to the following DHCPv6 features:

• Administrators can create IPv6 address scopes by simply specifying an IPv6 subnet prefix. The Windows DHCPv6 stateful server will automatically generate an IPv6 address for allocation to the client.
• The addresses generated by the DHCPv6 server are sparsely distributed over the available address space for that subnet. By randomly distributing the address over the large address range made available by a 64-bit IPv6 prefix, the Windows DHCP server makes it much harder to guess IPv6 network addresses.
• Clients can acquire a non-temporary and a temporary address through DHCPv6. A non-temporary IPv6 address can be used for Dynamic DNS registration, so that the client is "known" by that address. A temporary IPv6 address on the other hand can be used for establishing outgoing connections in scenarios where the client needs privacy for its non-temporary address private.
• Administrators can simplify the deployment by using the Router Advertisements to provide hints on whether to use DHCPv6 in the stateless or the stateful mode.
• The Windows DHCPv6 server will provide support for server authorization in Active Directory (AD). This will help reduce the possibility of a rogue server in managed domain environments.
• We recommend that administrators add reservations for clients with statically configured IPv6 address, so that those addresses are not inadvertently allocated to clients. In addition, administrators can configure a certain range of addresses as exclusions in order to ensure that these addresses are not assigned to clients.
• Administrators will also have access to other DHCP server functionality such as the capability for audit logging and use of the export/import commands to migrate DHCP server configuration and state information.

If you are interested in evaluating the Windows DHCPv6 server for your IPv6 deployment, we would love to have you participate in the Longhorn Server Beta program. If you are a Windows Server 2008 TAP customer, you will of course soon have access to the next IDS build in February which will contain the DHCPv6 Stateful server. Send me an email if you would like to participate in our beta program.

Santosh Chandwani

Windows Enterprise Networking