Friday, November 8, 2013

Windows Server 2012 - DHCP with IPv6 - server and scope options

There was much to examine about DHCP IPv6 in my previous post, so much that I omitted some elements.
 
For example: what is the DHCP IPv6 equivalent of the scope and server options? In particular the following:
 
- 003 - Router
- 006 - DNS Servers
- 015 - DNS Domain Name
 
 Indeed, if we look at DHCPv6 Server options, there is nothing, at first glance, that looks similar (please view the illustrations later in this blog post).
 
This is what I discovered.
 
 
003 - Router equivalent
 
First, in an IPv6 network, nodes are able to discover the default gateway (the router) automatically.
 
This reminded me of something I learned for the CCNA.
 
On one hand, IPv6 compatible routers advertise their presence to other nodes.
 
On the other, IPv6 nodes can solicit a router.
 
So, one way or another, the default gateway can be found, without any assistance from a DHCP server.
 
Therefore (it seems), there is no equivalent setting for "003 - Router" in DHCPv6.
 
In my practice network, I do not have a router that advertises itself or that other nodes can solicit.
 
Besides, I have disabled IPv4, resulting in a blank "Default Gateway" value (in the ipconfig output that can be viewed below - scroll).
 
 
 
006 DNS Servers and 015 DNS Domain Name equivalents

But now, let's remove the static DNS settings configured with the static IPv6 address fd00::15 and the static IPv6 address itself.
 
Accessing TCP/IP properties via ncpa.cpl (typed in "Run"), we can simply select: "Obtain an IPv6 address automatically" - and likewise for DNS.
 
 
Question: can an IPv6 client autoconfigure DNS settings?
 
It looks like it can try, producing (deprecated) fec0 entries:
 
C:\>ipconfig /all
 
Windows IP Configuration
 
   Host Name . . . . . . . . . . . . : PC1
   Primary Dns Suffix  . . . . . . . : machlinkit.biz
   [snip]
   DNS Suffix Search List. . . .. : machlinkit.biz
 
Ethernet adapter Local Area Connection:
 
   Connection-specific DNS Suffix  . : machlinkit.biz
   Description . . . . . . . . . . ..... : Intel(R) PRO/1000 MT Network Connection
   Physical Address. . . . . . . . . : 00-0C-29-F8-C0-46
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled .  : Yes
   IPv6 Address. . . . . . . . . ...... . : fd00::116b:fdfc:25ea:4350(Preferred)
   Lease Obtained. . . . . . . . . : Thursday, November 07, 2013 9:24:26 PM
   Lease Expires . . . . . . . . . . : Tuesday, November 19, 2013 9:24:26 PM
   Link-local IPv6 Address . . . . . : fe80::e07e:50de:a86e:edc7%11(Preferred)
   Default Gateway . . . . . . . . . :
   DHCPv6 IAID . . . . . . . . . . . : 234884137
   DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-17-5D-69-C3-00-0C-29-F8-C0-46
   DNS Servers . . . . . . . . . . . : fec0:0:0:ffff::1%1
                                                 fec0:0:0:ffff::2%1
                                                 fec0:0:0:ffff::3%1

 
Note: for clarity and concision, to get "straight to the point", I have removed some of the ipconfig output.
 
The use of "fec0" is probably not recommended - and only present for lack of static configuration or DHCP automatic configuration.
 
 
 
IPv6 options 00023 and 00024

My research leads me to believe that the "00023 - DNS Recursive Name Server IPv6 Address" is the equivalent of "006 - DNS Server".
 
Moreover, "00024 - Domain Search List" is similar to "015 - DNS Domain Name"

I'll configure 00023 like this:
 

 

Here is the result:

Windows IP Configuration
 
   Host Name . . . . . . . . . . . . : PC1
   Primary Dns Suffix  . . . . . . . : machlinkit.biz
   [snip]
   DNS Suffix Search List. . . . . . : machlinkit.biz
 
Ethernet adapter Local Area Connection:
 
   Connection-specific DNS Suffix  . : machlinkit.biz
   Description . . . . . . . . . . . : Intel(R) PRO/1000 MT Network Connection
   Physical Address. . . . . . . . . : 00-0C-29-F8-C0-46
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
   IPv6 Address. . . . . . . . . . . : fd00::33e5:ab3e:cd63:a38e(Preferred)
   Lease Obtained. . . . . . . . . . : Thursday, November 07, 2013 9:45:21 PM
   Lease Expires . . . . . . . . . . : Tuesday, November 19, 2013 9:45:21 PM
   Link-local IPv6 Address . . . . . : fe80::e07e:50de:a86e:edc7%11(Preferred)
   Default Gateway . . . . . . . . . :
   DHCPv6 IAID . . . . . . . . . . . : 234884137
   DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-17-5D-69-C3-00-0C-29-F8-C0-46
   DNS Servers . . . . . . . . . . . : fd00::10

 
So, the 00023 option does indeed configure the DNS server setting.
 
 
I'll configure 00024 like this:
 
 
 
 
 
Here is the result:
 
Windows IP Configuration
 
   Host Name . . . . . . . . . . . . : PC1
   Primary Dns Suffix  . . . . . . . : machlinkit.biz
   [snip]
   DNS Suffix Search List. . . . . . : machlinkit.biz
                                                     machlinkit.net
 
Ethernet adapter Local Area Connection:
 
   Connection-specific DNS Suffix  . : machlinkit.biz
   Description . . . . . . . . . . . : Intel(R) PRO/1000 MT Network Connection
   Physical Address. . . . . . . . . : 00-0C-29-F8-C0-46
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
   IPv6 Address. . . . . . . . . . . : fd00::c896:5dbb:b8f9:636a(Preferred)
   Lease Obtained. . . . . . . . . . : Thursday, November 07, 2013 9:54:33 PM
   Lease Expires . . . . . . . . . . : Tuesday, November 19, 2013 9:54:33 PM
   Link-local IPv6 Address . . . . . : fe80::e07e:50de:a86e:edc7%11(Preferred)
   [snip]
   DNS Servers . . . . . . . . . . . : fd00::10
   NetBIOS over Tcpip. . . . . . : Disabled

   Connection-specific DNS Suffix Search List :
                                       machlinkit.biz
                                       machlinkit.net

So, the 00024 option does indeed configure the domain names that the client will use for name resolution.
 
*
This concludes my experiments with DHCP and IPv6 - for now...

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