Network Configuration in Windows 7

Windows 7 includes GUI network configuration dialogs that are similar to those for Windows Vista. The IPv4 Properties dialog is similar to the one in Windows XP. They allow you to select automated configuration (DHCPv4 or SLAAC/DHCPv6) or Manual Configuration.

To use these tools, go to Control Panel / Network and Internet / Network Connections. You will see a list of available network interfaces:


network connections


Most likely, the connection to your main LAN will be called Local Area Connection.

If you right click on the Local Area Connection icon and select Status, you will see the following dialog:


local area connection status


This shows you whether you have connection to the IPv4 Internet and/or the IPv6 Internet, and whether the media is enabled (network carrier sense is active). It also shows how long your connection has been active, and the connection speed (e.g. 1.0 Gbps). It also shows the number of bytes sent and received on this interface.

To see more details of the interface status, click on Details. You will see the following:


status details


This has information similar to doing an ipconfig command in a Command Prompt window, but in the GUI system. You can scroll around in it, but you can't enlarge the window. It is never large enough to show all the details.

The Properties button in the Status dialog will take you to the Local Area Connection Properties dialog. You can also get there by right clicking on the Local Area Connection icon and selecting Properties from the pull-down menu.

However you get there, this is the Local Area Connections Properties dialog:


Local Area Connection Properties


In this dialog you can enable or disable Internet Protocol Version 6 (TCP/IPv6) and Internet Protocol Version 4 (TCP/IPv4). This is done by clicking on the protocol name. If the check box is present before the protocol name, the protocol is selected. You can use this dialog to make your node IPv4-only, IPv6-only, or Dual Stack (both selected).

You can enable or disable the other items, but only the two Internet Protocol items have configurable properties.


IPv4 Configuration

If you double click on Internet Protocol Version 4 (TCP/IPv4), you will get the IPv4 configuration dialog:


IPv4 Properties


If you want to obtain your IPv4 node address, subnet mask and default gatewayfrom DHCPv4, select Obtain an IP address automatically. If you want to manually specify those items, select Use the following IP address, then enter your desired settings in the input boxes. If you select the manual configuration, the Obtain DNS server address automatically option will be disabled.

Assuming you selected Obtain an IP address automatically, you can choose to also obtain the IPv4 addresses of DNS from DHCPv4 by selecting Obtain DNS Server address automatically.

Assuming you selected manual address configuration, or if you chose automatic address configuration but chose to enter DNS addresses manually, you can enter one or two IPv4 addresses for DNS in the lower input boxes.

If you want, you can have your settings validated upon exit.

You can also do advanced configuration (edit existing settings, specify more than one IPv4 node address, specify more than two IPv4 addresses of DNS, etc) by clicking the Advanced button. One of the advanced options is whether your node will try to use Dynamic DNS Registration to register the node's IPv4 address on the specified DNS servers. This assumes that the DNS servers have been configured to accept Dynamic DNS Registration from your nodes. There is no way in the GUI tools to specify a TSIG key for this. By default, Windows nodes will try to do Dynamic DNS Registration.


IPv6 Configuration

Now back on the Local Area Connections Properties dialog, if you double click on Internet Protocol Version 6 (TCP/IPv6), you will get the IPv6 configuration dialog:


IPv6 Properties 


Microsoft tried to make this look and feel like the IPv4 configuration, but Ipv6 doesn't really work the same way.

First, your node will autonomously generate a Link-Local unicast address all by itself. If your node has the Randomize Identifiers option enabled (which it is by default), the Interface Identifier of this address will be randomly generated. If the Randomize Identifiers option is disabled, the Interface Identifier of this address will be generated from your interface's MAC address, using the EUI-64 algorithm. Your node will then use Duplicate Address Detection to verify that the Link-Local address is unique on the link. The Windows GUI tool does not even mention the Link-Local unicast address, or allow you any control over it.

Second, assuming there is a source of Router Advertisement messages in your subnet and your node has the Router Discovery option enabled, whether you select Obtain an IPv6 address automatically or Use the following IPv6 Address,your node will do Stateless Address Autoconfiguration. This means it will obtain the Link-Local default gateway for your subnet using Router Discovery. Assuming the Router Advertisement message contains at least one Prefix Information Option, your node will then generate one Global Unicast address for each advertised prefix, using the Interface Identifier from the autonomously generated Link-Local unicast address and the normal Preferred and Valid lifetimes. If your node has the Temporary Address option enabled, it will generate a second Global Unicast address for each advertised prefix, but with shorter preferred and valid lifetimes. Your node will perform Duplicate Address Detection on all generated addresses.

Third, if the M-flag in the Router Advertisement message was set, or the M-flag is clear but the O-flag is set and there is a DHCPv6 server or relay agent in your subnet, then your node will obtain IPv6 addresses of DNS from the DHCPv6 server. If the M-flag is set, your node will obtain yet another Global unicast address from the DHCPv6 server, with a lease.

All this happens regardless of your choice in the first section of the IPv6 Properties dialog. The only difference is that if you select the Use the following IPv6 address, then you can manually configure yet another Global unicast address, the prefix length (virtually always 64), and a default gateway address. The preferred and valid lifetimes for this address will be infinite, and you completely control the address prefix and suffix (but the address will only work if you use a valid prefix). Your node will perform Duplicate Address Detection. Your configuring another Global address does not make the other addresses go away (like it does with IPv4 configuration).

Likewise, if you configure a default gateway address, that will be in addition to the one obtained via Router Discovery (unless it is the same address). You can specify the default gateway to be the Global Unicast address of the inside NIC of your gateway, but it is better to specify the Link-Local address of that NIC. If you specify the Global Unicast address, you will wind up with two IPv6 default gateways, which can cause problems (for example, guest OSes running in VirtualBox might be unable to communicate over IPv6.

On the other hand, certain things can make a windows node "lose" the default gateway obtained via Router Discovery. It is a good idea to configure it manually, especially on a Windows Server node. You should not enter a zone ID for a Link-Loca default gateway (it already knows what interface this is for). For example:


ipv6 properties 2


If you don't have DHCPv6 (or it doesn't advertise IPv6 addresses of DNS), you can manually configure one or two IPv6 addresses of DNS here as well. But unlike the node address, any manually configured address(es) for DNS will suppress the ones from DHCPv6.

As with the IPv6 GUI configuration tools, if you click on the Advanced button, you can configure more than one Global unicast address and control whether you node will try to use Dynamic DNS registration to register its IPv6 addresses in DNS. By default it does, which can lead to a very messy DNS. It is best to not let your nodes register all of their IPv6 addresses in DNS.

As you can see, the IPv6 GUI configuration tools are quite misleading, because IPv6 does auto-configuration very differently than IPv4 does. They should have completely redesigned the IPv6 GUI tools rather than trying to make them look like the IPv4 ones.

If you want to have only a single, managed IPv6 Global Unicast address, and no addresses generated by SLAAC, this is possible with manual configuration, but no existing auto-configuration tools can do this (until Sixscape DNMS).


Viewing Nework Configuration with ipconfig

In a Command Prompt window, you can use the ipconfig command to view the current network configuration. The IPv4 and IPv6 information is all mixed in randomly. This is typical output:

C:\Users\lhughes>ipconfig /all
Windows IP Configuration
   Host Name . . . . . . . . . . . . : Lawrence-PC
   Primary Dns Suffix  . . . . . . . : hughesnet.local
   Node Type . . . . . . . . . . . . : Hybrid
   IP Routing Enabled. . . . . . . . : No
   WINS Proxy Enabled. . . . . . . . : No
   DNS Suffix Search List. . . . . . : hughesnet.local
Ethernet adapter Local Area Connection:
   Connection-specific DNS Suffix  . : hughesnet.local
   Description . . . . . . . . . . . : Realtek PCIe GBE Family Controller
   Physical Address. . . . . . . . . : 50-46-5D-6B-7A-54
   DHCP Enabled. . . . . . . . . . . : No
   Autoconfiguration Enabled . . . . : Yes
   IPv6 Address. . . . . . . . . . . : 2001:470:3d:3000::2:1(Preferred)
   IPv6 Address. . . . . . . . . . . : 2001:470:3d:3000::4:57db(Preferred)
   Lease Obtained. . . . . . . . . . : Thursday, August 15, 2013 8:53:44 PM
   Lease Expires . . . . . . . . . . : Tuesday, August 27, 2013 8:53:44 PM
   IPv6 Address. . . . . . . . . . . : 2001:470:3d:3000:2030:9139:9cd5:ab52(Pref
   IPv6 Address. . . . . . . . . . . : fda4:73c2:e5b8:1000:2030:9139:9cd5:ab52(P
   Temporary IPv6 Address. . . . . . : 2001:470:3d:3000:7184:6098:5708:fe4e(Pref
   Temporary IPv6 Address. . . . . . : fda4:73c2:e5b8:1000:7184:6098:5708:fe4e(P
   Link-local IPv6 Address . . . . . : fe80::2030:9139:9cd5:ab52%11(Preferred)
   IPv4 Address. . . . . . . . . . . :
   Subnet Mask . . . . . . . . . . . :
   Default Gateway . . . . . . . . . : fe80::290:bff:fe1b:5762%11
   DHCPv6 IAID . . . . . . . . . . . : 240141917
   DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-18-BA-30-56-50-46-5D-6B-7A-54
   DNS Servers . . . . . . . . . . . : 2001:470:3d:3000::14
   NetBIOS over Tcpip. . . . . . . . : Enabled
   Connection-specific DNS Suffix Search List :
Tunnel adapter isatap.{8C29F61F-7AFF-42E2-8535-F508C29EAAFC}:
   Media State . . . . . . . . . . . : Media disconnected
   Connection-specific DNS Suffix  . : hughesnet.local
   Description . . . . . . . . . . . : Microsoft ISATAP Adapter
   Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
   DHCP Enabled. . . . . . . . . . . : No
   Autoconfiguration Enabled . . . . : Yes
Tunnel adapter Teredo Tunneling Pseudo-Interface:
   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Teredo Tunneling Pseudo-Interface
   Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
   DHCP Enabled. . . . . . . . . . . : No
   Autoconfiguration Enabled . . . . : Yes
   IPv6 Address. . . . . . . . . . . : 2001:0:9d38:6ab8:3829:21a1:53eb:fdfe(Pref
   Link-local IPv6 Address . . . . . : fe80::3829:21a1:53eb:fdfe%15(Preferred)
   Default Gateway . . . . . . . . . :
   NetBIOS over Tcpip. . . . . . . . : Disabled


 For a detailed explantion of this output, see A Tour of IPv6 on Windows.