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IP address configurations in DHCP RRS feed

  • Question

  • Howdy - I haven't had to setup DHCP in server 2012/2016 in a redundant manner yet.  I see how you configure the servers in high availability mode.  This all makes sense.

    One thing that doesn't is the IP scheme.  It doesn't use a windows high availability cluster or anything, so the two servers don't share an IP.  If I have a pair of servers setup in Load Balance mode with IPs of:

    Server1.home.local - 10.0.1.11

    Server2.home.local - 10.0.1.12

    Our networking team only wants to put in 1 IP address helper in our routers.  I basically have to pick one or the other, don't I?  There isn't an IP they share....

    We do have netscalers onsite.  I could load balance UDP ports 67 between the two above addresses and name it 10.0.1.13.  That could be the DHCP address.

    Is there something I"m missing with the setup?  I appreciate how they are hot failover, but if they don't share addressing, when will the 'second' server ever get used if we only configure scopes with the 'first' server?

    Wednesday, March 21, 2018 2:10 PM

All replies

  • Hi,

    Have a nice day! Thanks for your question.

    To have a better understanding about this issue, please help me to collect more information:

    1. >> Our networking team only wants to put in 1 IP address helper in our routers.  I basically have to pick one or the other, don't I?  There isn't an IP they share…

    We do have netscalers onsite.  I could load balance UDP ports 67 between the two above addresses and name it 10.0.1.13.  That could be the DHCP address.

    What’s the meaning of this point? Which function would you configure the routers?

    1. Have you setup the two DHCP servers in load balance?

    Here is the links refer to DHCP failover communications, it may be helpful,

    DHCP Failover Communications

    https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2012-R2-and-2012/dn338987(v=ws.11)

    https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2012-R2-and-2012/dn338973(v%3dws.11)

    Highly appreciate your successive effort and time. If you have any questions and concerns, please feel free to let me know.

    Best regards,

    Michael


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    Thursday, March 22, 2018 10:01 AM
  • Howdy - Thanks for the reply!

    I'm not a networking guy - but from my understanding when a DHCP server isn't in your subnet, you need to assign an IP Address helper on the switchgear for each subnet so the router knows where to forward DHCP requests. 

    IN a failover, you have two servers with two separate IPs.  I'm confused how you have DHCP run with two separate IPs?

    Thursday, March 22, 2018 1:25 PM
  • Hi,

    Thanks for your update.

    For your first question, when a DHCP server isn't in your subnet, you may deploy a DHCP Relay Agent. A DHCP relay agent is any host that forwards DHCP packets between clients and servers. Relay agents are used to forward requests and replies between clients and servers when they are not on the same physical subnet. I encountered a similar case. Please try the following link:

    https://social.technet.microsoft.com/Forums/windowsserver/en-US/cf4ef862-c30b-405a-9f86-c93f524a77ab/dhcp-server-for-2-subnet-network?forum=winserveripamdhcpdns

    Deploy a DHCP relay agent:

    https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/ff687684(v=ws.10)

    https://www.sqa.org.uk/e-learning/NetInf101CD/page_76.htm

    Since I'm not familiar with third party product Router or Switch, I couldn't provide this experience. And you are also professional at networking. Exactly right! Some routers and Layer3 Switch are supporting for DHCP broadcast currently according to RFC 1542.

    You may refer to the following link:

    https://www.rfc-editor.org/rfc/rfc1542.txt

    Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information. 

    Furthermore, for your second question, you could configure multiple scopes which are separating addresses pools on one DHCP server. Haven't had to set DHCP failover with two DHCP servers.

    Hope above information can help you. I look forward hearing your good news. 

    I appreciate your successive effort and time. If you have any questions or concerns, don’t hesitate to let me know.

    Wish you have a nice weekend!

    Best regards,

    Michael



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    Friday, March 23, 2018 9:26 AM
  • Hi,

    How are things going on? Was your issue resolved?

    Please let us know if you would like further assistance.

    Wish you have a nice day!

    Best regards,

    Michael


    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com

    Monday, March 26, 2018 9:40 AM
  • Hi Steve,

    How are things going on? Was your issue resolved?

    Please let us know if you would like further assistance.

    Wish you have a nice day!

    Best regards,

    Michael


    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com

    Wednesday, March 28, 2018 9:14 AM
  • Hi Steve,

    How are things going on? Was your issue resolved?

    Please let us know if you would like further assistance.

    Wish you have a nice day!

    Best regards,

    Michael


    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com

    Friday, March 30, 2018 11:36 AM