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How does DHCP superscope load balance between child scopes?

    問題

  • Due to sudden size growth we have had to setup two different subnets on one physical network.  One is a /24 and the new one is a /23.  Both were created as child scopes in a superscope.

    My understanding is that now I am dealing with what is termed a "multinet" and the DHCP clients simply broadcast their DHCP request and there is no DHCP Relay or routers involved.

    So how does the DHCP pass out requests from my two child scopes?  I would imagine it would load balance in some round robin fashion or something similar but that is not what I am seeing.

    My original scope still appears to max out all the time with 100% utilization of ip's, while the new scope is occasionally used.  So far I have not seen anyone unable to obtain an ip address, but we just implemented this superscope today so I am concerned that I don't have something setup correctly.

    2012年6月18日 下午 10:26

解答

所有回覆

  • There may be overlap with the scopes, since a /23 gives you 512 IPs, and a /24 gives 256, and some of them can be overlapping, but I don't know since you didn't post the subnets and lease ranges ior anyother specifics.

    See if these links help:

    Technet thread: "What's a SuperScope?" 11/17/2011
    Good info on what a Superscope is and other links.
    http://social.technet.microsoft.com/Forums/en-US/winserverNIS/thread/ea565626-d32a-43b5-9946-c4eb9a4e1c2d

    Using superscopes
    http://technet.microsoft.com/en-us/library/cc757614(WS.10).aspx

    Configuring a DHCP Superscope
    Applies to Windows 2008 R2
    http://technet.microsoft.com/en-us/library/dd759168.aspx

    Using DHCP "Superscopes" to Serve Multiple Logical Subnets (For NT4, but applies to all Windows Server versions)
    http://support.microsoft.com/kb/161571 

    .

    What I can suggest the best thing to do is to wipe out both scopes and start fresh. Is that something you are able to do?

    .


    Ace Fekay
    MVP, MCT, MCITP EA, MCTS Windows 2008/R2, Exchange 2007 & Exchange 2010, Exchange 2010 EA, 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 post is provided AS-IS with no warranties or guarantees and confers no rights.

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    2012年6月18日 下午 11:48
  • Sorry Ace  the subnets are:

    10.0.250.0/23

    172.30.1.0/24

    Wiping out both scopes is not really an option at this point except as a last resort.

    2012年6月19日 下午 03:06
  • Sorry for the late reply. Busy!

    So there is no overlap, but they are not in subnet mask succession. They should be in succession, such as 192.168.1.0/24, 192.168.2.0/24, etc. The two you posted are completely different. I haven't done it that way, and I'm not sure if it will work.

    Did any of the links I provided help?

    .


    Ace Fekay
    MVP, MCT, MCITP EA, MCTS Windows 2008/R2, Exchange 2007 & Exchange 2010, Exchange 2010 EA, 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 post is provided AS-IS with no warranties or guarantees and confers no rights.

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    2012年6月22日 下午 04:19
  • Thanks Ace.  Unfortunately, having consecutive subnets is not an option unless we were to move to a totally new subnet range which is next to impossible because of the number of networks we service and the routing/ACL changes that would be required.

    Just to let you know the DHCP server does work with the two non-consecutive subnets.  The only issue is that it appears that the server will only start handing out ip's from the 10.0.250.0 scope once the original 172.30.1.0 scope is 100 utilized.  I am not 100% certain on this, but should know more this coming Monday.

    Ace I have actually read all of those links in my search before I came here and I am amazed how cloudy and contradictory the information on superscopes is presented.  If I discover the answer the hard way I will be sure to report back.

    2012年6月22日 下午 04:56
  • I'm thinking DHCP is handing out IPs based on the longer network bits, which is why 172.x.x.x range is used first. This is the same way subnet priortization works. If there is no direct subnet match, it uses the longest network bits first in deciding which response to give during a query. Therefore, it appears DHCP is hardcoded wtih the same algorithm. I know how to change it for DNS in the reg, but not DHCP.

    .

    You can contact Microsoft support if you feel this information was not helpful. Their engineers can explain it better than I can, and can possibly provide a work around or resolution. Here's the link with the phone numbers to get you started if you choose this option:
    http://support.microsoft.com/default.aspx?scid=fh;EN-US;PHONENUMBERS 

    .


    Ace Fekay
    MVP, MCT, MCITP EA, MCTS Windows 2008/R2, Exchange 2007 & Exchange 2010, Exchange 2010 EA, 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 post is provided AS-IS with no warranties or guarantees and confers no rights.

    FaceBook Twitter LinkedIn

    2012年6月22日 下午 05:48