Tuesday, August 12, 2014

Changing the Reserved IP Address in a Static DHCP Reservation in Windows Server


Static IPs preferred

DHCP is a good thing if it works - set and forget. But what happens if the DHCP server is down for some reason? Exactly - the whole network stops working. Another problem of DHCP are those random IPs a client gets each time. This is very bad for printers that use DHCP. Therefore I prefer static IPs over dynamic.


Windows Server 2012 R2 Essentials: You cannot stop Windows LAN Configuration Service anymore

Unfortunately, there is some strange behavior on Server 2012 R2 Essentials if you just enter static IPs on your Windows clients - your Windows OS will show exclamation marks on your network connection from time to time, etc. There is actually a Windows Server LAN Configuration service which keeps overwriting your manual settings and the bad thing is that you cannot stop that service in Server 2012 R2 any more for some reason...So, instead, I decided to use DHCP on the server and add an Alternative IP Configuration with all static data as a fallback if my server is down. This "alternative configuration" becomes available in the client's IP Settings as a new tab as soon as you enable automatic DHCP configuration on the main tab.


Creating Static DHCP Entries in Windows Server

So DHCP is running but I still need static IPs that don't change. To achieve this in Windows Server DHCP configuration I need to find the leases, right click and convert them to static reservations. Then under reservations if I look at the properties I see that now my client will always get a static IP. But wait! This IP is set by my DHCP server and not by me. What if I want to change that IP as I like? E.g. I want it to be the same as the static IP I have set in the alternate IP configuration on my clients as described above. But it is greyed out for some reason - only Microsoft knows why. Sometimes I wonder how stupid programmers can be. Oh sure, it is more important to add new stupid features to a server OS than making the everyday features we use work more efficiently.

I googled around and even found this Microsoft Technet Howto from 2005 (!) regarding Windows Server 2003 (!):


It states:

The IP address in an existing client reservation cannot be modified directly. To achieve similar results, the existing reservation must be deleted and a new reservation added.
How stupid is that?!?!?!


Changing the Reserved IP Address

So, to make my desired static IPs work with DHCP I need to go through these "simple" steps (thank you Microsoft!):
  1. Open the DHCP configuration on my Windows Server
  2. Find the address lease for the particular client - this is some random IP the DHCP server gave to my client
  3. Create a reservation form that lease (right click + add to reservations)
  4. Find the new reservation under reservations
  5. Open reservation properties by right clicking - PROBLEM: IP is still "random", defined by the DHCP server and it is grayed out - can't change it!
  6. Create and open a text file...
  7. Manually copy the host name and the MAC address form the fields to my text file
  8. Delete this reservation - isn't that stupid?
  9. Create a new reservation by right clicking on reservations - once again...
  10. Copy and paste the hostname and the MAC address from the text file to the fields of the new reservation
  11. Finally: Enter your desired IP for the new reservation - that's all we wanted to achieve
Again: How complex is that Microsoft? Every modern router is easier to configure.

Hope this helps!