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Server 2012 with DHCP Load Balancing using IP Helper

    Question

  • Forgive me for my ignorance but I was wondering if you gents could help me understand the process for how the client and server works in the following scenario:

    - 2 geographical sites

    - Router at each site with IP Helper feature

    - 2 x Server 2012 (DC1 and DC2) configured in DHCP Failover Load Balanced Mode

    Question 1

    What address do you specify on the router for IP helper - DC1, DC2, both or a host name that covers both DCs?

    My understanding is that when the client requests an IP, it goes to both DHCP servers and only one responds based on MAC hash alogrithm. What I am wondering is how do you get the IP helper to send one request to both servers OR do you simply specify DC1 and it will work out the load balancing from receiving the request? Bit confused.

    Question 2

    In the above scenario, say you have DC1 die and you have a 50/50 setting applied. Can DC2 then take over the scope for the dead DC1 and operate as the one main DHCP server for both? 

    So I guess I am asking is can you be load balanced (active/active) AND be Hot standby at the same time in a DHCP Failover? or is it one or the other?

    Thank you


    Tuesday, August 20, 2013 6:03 PM

Answers

  • Hi, In my understanding, the dhcp loadbalancing does not share a virtual ip, like a ts clustering.

    That imply you will have to configure both iphelper adress in the remote router. The IP used would be the one of the two DHCP server that answer first.

    For your other question I will let someone else answer, as I'am less used to that. (but I would tend to guess the both DHCP server will broadcast to each other what IP they leased to not have duplicate dhcp offer.. so if it's the case, the other DHCP can take the lead as it will know where to continue it's work)


    MCP | MCTS - Exchange 2007, Configuring | Member of TechNet Wiki Community Council | French Moderator on TechNet Wiki (Translation Widget)

    Wednesday, August 21, 2013 2:53 AM
    Moderator
  • Hi,

    The first question: Based on my knowledge both of the DCs should be specified, otherwise the failover would be useless.

    Second:DC2 would take the entire scope if DC1 is down.

    For more information:

    DHCP Failover Load Balance Mode

    http://blogs.technet.com/b/teamdhcp/archive/2012/08/06/dhcp-failover-load-balancing-mode.aspx

    DHCP Failover Hot-Standby Mode

    http://blogs.technet.com/b/teamdhcp/archive/2012/09/03/dhcp-failover-hot-standby-mode.aspx

    Hope this helps

    Wednesday, August 21, 2013 9:27 AM
    Moderator

All replies

  • Hi, In my understanding, the dhcp loadbalancing does not share a virtual ip, like a ts clustering.

    That imply you will have to configure both iphelper adress in the remote router. The IP used would be the one of the two DHCP server that answer first.

    For your other question I will let someone else answer, as I'am less used to that. (but I would tend to guess the both DHCP server will broadcast to each other what IP they leased to not have duplicate dhcp offer.. so if it's the case, the other DHCP can take the lead as it will know where to continue it's work)


    MCP | MCTS - Exchange 2007, Configuring | Member of TechNet Wiki Community Council | French Moderator on TechNet Wiki (Translation Widget)

    Wednesday, August 21, 2013 2:53 AM
    Moderator
  • Hi,

    The first question: Based on my knowledge both of the DCs should be specified, otherwise the failover would be useless.

    Second:DC2 would take the entire scope if DC1 is down.

    For more information:

    DHCP Failover Load Balance Mode

    http://blogs.technet.com/b/teamdhcp/archive/2012/08/06/dhcp-failover-load-balancing-mode.aspx

    DHCP Failover Hot-Standby Mode

    http://blogs.technet.com/b/teamdhcp/archive/2012/09/03/dhcp-failover-hot-standby-mode.aspx

    Hope this helps

    Wednesday, August 21, 2013 9:27 AM
    Moderator