Windows Server 2012 is fast approaching and from the RC that is available its going to be awesome. Now I’ve been looking into an area that has traditionally changed very little since Windows 2000. DHCP has remained fairly constant but with Windows Server 2012 there are 2 great new additions to the DHCP role. One feature is DHCP failover where 2 DHCP servers can either be configure to load balance the DHCP process or one server can take over from another should the active DHCP server go into a failure state. The feature I will be discussing here though in DHCP policies, policies can be set to assign DHCP IP addresses based on criteria of the client pc.
First off this blog post is based on the RC version of Windows Server 2012 so the feature may change or completely disappear in the actual release.
DHCP policies allow you to allocate IP addresses and scope options based upon details that the client sends when performing the Discover task of the DORA (Discover Offer Request Accept) process. This means that you could for example give a certain range of IP addresses and scope options to either specific MAC addresses, or Vendor/User class, Client ID or Relay Agent Information. This would be really handy if you had a number of different thin clients from say HP and Wyse and you can set policies to direct the clients to different FTP servers to receive their device configuration.
Lets work through an example to show you the power of DHCP policies.
To configure DHCP policies click TOOLS\DHCP within the Server 2012 server manager and expand the DHCP node to show the policies.
Right Click and choose Activate to enable the DHCP policy then right click and choose new policy.
Give the policy a name and a description then click next.
The next screen is where you configure what the policy will apply to.
Click the Add button to start building your policy matching in this instance we will match the policy to a MAC address of a client pc.
The next screen allows you to specify a range of IP addresses to allocate to the client machine that matches this policy. You can also use the default address range defined in the dhcp scope by clicking the NO radio button. For example if you had a range of 192.168.168.100 to 192.168.168.200 defined in your default scope you could carve that up in this screen to to allocate IP addresses from 192.168.168.180 to 192.168.168.200 to clients that match this policy. In fact within this screen it wont let you proceed until you specify a valid subrange (if you will) unless you click the NO radio button so typing 172.16.10.100 to 172.16.10.200 is not allowed for example and you will receive the “No valid range” error .
The next screen allows you configure the scope options for the policy so here is where you can identify different DNS servers FTP servers default gateways etc for clients matching this policy. When configuring DNS options within this window it will automatically try to validate the DNS configuration by performing a DNS lookup to the specified server.
The next screen is the summary screen where you see all the policies configuration click finish when you are happy with the settings. The policy is then active straight away although the policy on already powered on clients will not take effect until the next DHCP refresh interval is passed on the client and it tries to renew its DHCP lease.
Pretty cool eh!