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DHCP Failover

    Question

  • in numerous sites, including official microsoft w2k8r2 documents, there is information about a new feature of DHCP - DHCP Failover.
    i tried to find any information in the system, documentation, netsh etc how to configure it. the question is:
    - is this feature implemented or it's just palnned to be done?

    thx for any information

    -o((: nExoR :))o-
    Monday, February 23, 2009 11:50 AM

All replies

  • Hi,

    DHCP Failover can be achieved via the use of clusters or, to a certain extent, the 80/20 scope split rule. Some notes pertaining to these two options are found in the following links:

    http://technet.microsoft.com/en-us/library/dd296696.aspx
    http://technet.microsoft.com/en-us/library/dd296651.aspx

    Regards,

    Salvador Manaois III
    MCITP | Enterprise & Server Admin
    MCSE MCSA MCTS CIWA C|EH
    Bytes & Badz: http://badzmanaois.blogspot.com
    Tuesday, February 24, 2009 2:59 AM
  • Hi,

    This is a feature of Windows 2008 R2 only. For other Windows server versions, dhcp failover is achieved in the way that Salvador said. I also did not find specific technical documents about it.
    Have a nice day! The Masterplan - MCSE,MCITP-EA http://winmasterplan.blogspot.com
    Tuesday, February 24, 2009 12:48 PM
  •  http://www.ravenreport.com/blog/post/Windows-2008-R2-to-Support-DHCP-Failover.aspx

    &
    http://tools.ietf.org/html/draft-ietf-dhc-failover-12

    UPDATE: As indicated in the linked blog article, this feature was removed from the Windows 2008 R2 feature set .  As of today (July 2011) there is no DHCP fail-over feature outside of Windows Clustering or the 80/20 rule.




    Mike Crowley: MCT, MCSE, MCTS, MCITP: Enterprise Administrator / Messaging Administrator
    Wednesday, February 25, 2009 8:16 PM
  • The feature of “DHCP Failover” was discussed upon in the early planning phases of Windows Server 2008 R2 and dropped of eventually.The decision is to continue to support the DHCP Failover with the clustering technology available in Windows platform.In Windows Server 2008 R2,  the clustering of DHCP is made as robust as possible.

    Monday, March 30, 2009 11:09 AM
  • If this officially being pulled out from the final release, if so are there any plans from Microsoft to offer DHCP resiliance in the future (aside from split-scope or clustering) i.e. replicated database across all DC's or DHCP servers. Could Microsoft not provide DHCP as an applience (like many other vendors which do not fully integrate into the Microsoft portfolio....?).

    This gives us little alternative other then moving to 3rd party suppliers as pressure falls to offer a fully resiliant service.

    My only solution (if feasable) is to continue using Microsoft DHCP but as a VM in VMWare's vSphere 4 or ESX4 (Realease Date TBC) and enabling the Fault Tolarance feature...

    If anyone has thoughts on this please feel free to add...

    ................Y

    Friday, May 15, 2009 8:46 AM
  • For DHCP failover, check out Infoblox (https://solutionfinder.microsoft.com/Solutions/SolutionDetailsView.aspx?solutionid=017b28ead51a4279bc7956190e9ddef3&Partnerid=69887933-5bd2-4c0a-ad0c-dd7b9ccd7b98&wa=wsignin1.0).  It has DHCP failover and integrates directly with Microsoft for DNS management, IP address management, etc.

    It also offers HA which is similar to clustering but it doesn't require external disk configurations.

    • Proposed as answer by dsmith72 Tuesday, May 04, 2010 8:30 PM
    Tuesday, May 04, 2010 8:30 PM
  • I know of infoblox that it can work together with windows 2008, i gave a infoblox training.

    And looking under the hood at windows 2008 in powershell there seam to be some left overs.
    Set-DHCP4failover.
    Like infoblox it seams to be supported for dhcp4 but not for ip6, (ip6 doesnt need it).
    Nt sure how the command should be used dough.
    I am wondering if MS actually does support it, but not in a GUI version. A reason why infoblox can do it with 2008.

    From my observations working with MS for many years now MS has made a great IP stack, while linux has a more glue-ed broken parts approach, you can glue everything together, it doesn't rule out that MS cannt do it.
    They did things in the past Unix people or Novell people thought to be impossible, as i had such discussions with colleagues.


    On the other hand looking at exchange, i dont have the feeling that MS is still thinking that the GUI should be the place to do everything, but only basic administration. More and more a server has become an environment for programmers, and a few people are picking it up by learning power-shell. (
    The beloved and hated power shell is the fixit glue from MS


    :))

    Monday, January 09, 2012 1:36 PM
  • Yeah there is a good article for this task. visit this link

    http://technet.microsoft.com/en-us/library/ee405263%28WS.10%29.aspx

     

    Administrator

    www.techfindings.com

    Thursday, January 12, 2012 10:19 AM
  • The 80/20 rule, as already mentioned, is your best bet. This was also heavily discussed a few days ago in the DS forum. You might find it extremely informative.

    TechNet Thread - "DHCP - Load Balance?"
    http://social.technet.microsoft.com/Forums/en-US/winserverDS/thread/d0d6b210-c57c-4a05-8763-a6a67895ace5

     

    You'll find lots of good info in that thread. Also, I was aware that the clustering feature was going to be introduced with Windows 8, but it was pulled. Maybe the next release or an SP release... :-)

    Ace

     


    Ace Fekay
    MVP, MCT, MCITP Enterprise Administrator, MCTS Windows 2008 & Exchange 2007 & Exchange 2010, Exchange 2010 Enterprise Administrator, MCSE & MCSA 2003/2000, MCSA Messaging 2003
    Microsoft Certified Trainer
    Microsoft MVP - Directory Services
    Complete List of Technical Blogs: http://www.delawarecountycomputerconsulting.com/technicalblogs.php

    This posting is provided AS-IS with no warranties or guarantees and confers no rights.

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    • Proposed as answer by ObiWan Friday, January 13, 2012 8:43 AM
    Thursday, January 12, 2012 7:18 PM
  • The 80/20 rule, as already mentioned, is your best bet. This was also heavily discussed a few days ago in the DS forum. You might find it extremely informative.

    TechNet Thread - "DHCP - Load Balance?"
    http://social.technet.microsoft.com/Forums/en-US/winserverDS/thread/d0d6b210-c57c-4a05-8763-a6a67895ace5

    Ace... there's another option too :) and although it has pros and cons and can't be always implemented, I think it may be worth mentioning it; the idea is to setup the two DHCP servers in a 100/100 config :D yes, I'm not becoming crazy... basically what you'll need for such a config is changing the netmask to include at least two times the IPs you need, at that point you'll setup your two DHCP servers to offer exactly one half of the available IPs (that is all the IPs really needed :D !); with such a config you won't need to worry about delays or which DHCP is serving a given request since either DHCP server will have enough IP to cover the requests from all the hosts.

    Just to be more clear, let's say we use a 10.0.0.0/24 subnet (255.255.255.0); in this case, our hosts addresses will range from 10.0.0.1 to 10.0.0.254; till now nothing special (let aside reservation and the like - just to keep things simple), now, we want to setup a redundant DHCP config, we know we will need a max of 254 hosts (as for the range we already saw), so we start by changing the netmask and widening the subnet; in this case we'll change the netmask to become a /23 (255.255.254.0) so, the new 10.0.0.0/23 subnet will allow IPs ranging from 10.0.0.1 to 10.0.1.254, that is, a total of 510 hosts; at this point, we'll setup our two DHCP server scopes so that the first DHCP will serve addresses from 10.0.0.1 to 10.0.0.254 and the second DHCP will serve the range 10.0.1.1 to 10.0.1.254; as it's easy to see, either DHCP server will now be able to serve ALL the needed IP addresses :)

    As I wrote the above may solve the issue, but then one should also verify if the current network infrastucture will allow changing the netmask without issues, so, a setup like the above should be carefully evaluated before deciding to implement it.

    A final note; the above setup may also allow to configure four DHCP servers; in such a case you may setup each couple of servers using the 80/20 rule (on a given subnet range - as above); by the way, in such a case you may also want to deal with latency... although it won't be mandatory nor as important as with a regular 80/20 setup

     


    • Edited by ObiWan Friday, January 13, 2012 8:44 AM
    • Proposed as answer by Ace Fekay [MCT]MVP Friday, January 13, 2012 7:00 PM
    Friday, January 13, 2012 8:42 AM
  • The 80/20 rule, as already mentioned, is your best bet. This was also heavily discussed a few days ago in the DS forum. You might find it extremely informative.

    TechNet Thread - "DHCP - Load Balance?"
    http://social.technet.microsoft.com/Forums/en-US/winserverDS/thread/d0d6b210-c57c-4a05-8763-a6a67895ace5

    Ace... there's another option too :) and although it has pros and cons and can't be always implemented, I think it may be worth mentioning it; the idea is to setup the two DHCP servers in a 100/100 config :D yes, I'm not becoming crazy... basically what you'll need for such a config is changing the netmask to include at least two times the IPs you need, at that point you'll setup your two DHCP servers to offer exactly one half of the available IPs (that is all the IPs really needed :D !); with such a config you won't need to worry about delays or which DHCP is serving a given request since either DHCP server will have enough IP to cover the requests from all the hosts.

    Just to be more clear, let's say we use a 10.0.0.0/24 subnet (255.255.255.0); in this case, our hosts addresses will range from 10.0.0.1 to 10.0.0.254; till now nothing special (let aside reservation and the like - just to keep things simple), now, we want to setup a redundant DHCP config, we know we will need a max of 254 hosts (as for the range we already saw), so we start by changing the netmask and widening the subnet; in this case we'll change the netmask to become a /23 (255.255.254.0) so, the new 10.0.0.0/23 subnet will allow IPs ranging from 10.0.0.1 to 10.0.1.254, that is, a total of 510 hosts; at this point, we'll setup our two DHCP server scopes so that the first DHCP will serve addresses from 10.0.0.1 to 10.0.0.254 and the second DHCP will serve the range 10.0.1.1 to 10.0.1.254; as it's easy to see, either DHCP server will now be able to serve ALL the needed IP addresses :)

    As I wrote the above may solve the issue, but then one should also verify if the current network infrastucture will allow changing the netmask without issues, so, a setup like the above should be carefully evaluated before deciding to implement it.

    A final note; the above setup may also allow to configure four DHCP servers; in such a case you may setup each couple of servers using the 80/20 rule (on a given subnet range - as above); by the way, in such a case you may also want to deal with latency... although it won't be mandatory nor as important as with a regular 80/20 setup

     



    Obi,

    Great suggestions, and very viable. I would suggest to post this to that other thread, too!

     


    Ace Fekay
    MVP, MCT, MCITP Enterprise Administrator, MCTS Windows 2008 & Exchange 2007 & Exchange 2010, Exchange 2010 Enterprise Administrator, MCSE & MCSA 2003/2000, MCSA Messaging 2003
    Microsoft Certified Trainer
    Microsoft MVP - Directory Services
    Complete List of Technical Blogs: http://www.delawarecountycomputerconsulting.com/technicalblogs.php

    This posting is provided AS-IS with no warranties or guarantees and confers no rights.

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    • Proposed as answer by ex MS Tuesday, January 17, 2012 11:16 AM
    Friday, January 13, 2012 7:01 PM
  • Obi,

    Great suggestions, and very viable. I would suggest to post this to that other thread, too!


    Thanks Ace and... just posted on the other thread, hope it may be useful.

    Just to explain it a bit... I faced some DHCP config time ago and I came out with such a 100/100 config while thinking at the RAID disk configurations; you may compare the 100/100 to the RAID-1 type of config (mirroring) :D and, if you want, you may compare the four servers config (two couples with 80/20 range on each network half) to something like the RAID-10 (or probably the RAID-50) :D

     

    Saturday, January 14, 2012 10:53 AM
  • I know this is an old thread, but I wrote a DHCP failover script that seems to work fairly well in our environment if anyone is interested. We have two DHCP servers on Server 2008 R2, a primary and backup. Our configuration is hot standby; that is, the backup server holds a copy of the database but doesn't activate unless the primary goes down. I put the script on Pastebin if anyone is interested. Run it as a scheduled task every 10 minutes (or whatever interval) on your backup DHCP server. http://pastebin.com/psVssn5w
    Tuesday, March 06, 2012 6:20 PM
  • I know this is an old thread, but I wrote a DHCP failover script that seems to work fairly well in our environment if anyone is interested. We have two DHCP servers on Server 2008 R2, a primary and backup. Our configuration is hot standby; that is, the backup server holds a copy of the database but doesn't activate unless the primary goes down. I put the script on Pastebin if anyone is interested. Run it as a scheduled task every 10 minutes (or whatever interval) on your backup DHCP server. http://pastebin.com/psVssn5w
    That my friend is a dam good script! Many Thanks. 
    Friday, March 16, 2012 3:26 PM
  • Related: 

    Test Lab Guide: Demonstrating DHCP Failover in Windows Server "8" Beta  

    http://www.microsoft.com/download/en/details.aspx?id=29017



    Mike Crowley | MVP
    My Blog -- Planet Technologies

    Monday, April 02, 2012 3:07 PM
  • Also see http://technet.microsoft.com/en-us/library/hh831385.aspx

    Step-by-Step: Configure DHCP for Failover

    Applies to Windows Server 8 Beta.

    Friday, May 11, 2012 6:16 AM
  • Fantastic script.  I am running it in production and I can tell you that it works flawlessly.  EXCELLENT.

    Adam

    Senior Systems Engineer


    • Edited by EvilBart Wednesday, October 17, 2012 2:00 AM
    Wednesday, October 17, 2012 1:59 AM
  • Related: 

    Test Lab Guide: Demonstrating DHCP Failover in Windows Server "8" Beta  

    http://www.microsoft.com/download/en/details.aspx?id=29017




    Was this something that was suppose to make it into the release and didn't as mentioned above because I don't see the failover option as mentioned in the lab
    Wednesday, December 05, 2012 8:55 PM
  • nevermind, I was reading server 8 as 2008. server 8 is basically server2012
    Wednesday, December 05, 2012 9:03 PM