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cons of standby mode or loadbalanced RRS feed

  • Question

  • Hi all

    I have 2 DHCP servers with load balanced failover relationship

    Settings as follow:

    Maximum client lead time =30 minutes

    Load balanced

    Local server =50%

    Partner server =50%

    State switch over =5 minutes

    According to my configuration:

    If one of the servers fails so the running server will be in communication interrupted state then after 5 minutes it will turn to partner down and after 30 minutes it will take control of the full scope but in this case it will renew IP lease for 30 minutes or respond to client request for new ip lease with 30 minutes too, Is this right?

    While the servers are running in load balanced mode and each of them has leased ip addresses,Could I change the failover relationship to standby mode

    What is the best configuration for MCLT?

    How to prevent the situation of both servers running in partner down state

    What is the drawback of standby mode and load balanced mode

    Sunday, January 6, 2019 6:18 PM

All replies

  • Hi,

    >>it will renew IP lease for 30 minutes or respond to client request for new ip lease with 30 minutes too, Is this right?

    Yes, that's how MCLT works.

    During the partner down state, for clients that did not previously have a lease, the running DHCP server will assign an IP address from its address pool. when the address pool is exhausted,  it will begin granting leases from the failover partner's IP address pool. For clients that previously had a lease, the running server will renew the same IP address for the client.

    The first lease issued by a DHCP server from a scope that belongs to a DHCP failover relationship is always for the MCLT duration. After this lease is renewed at half the lease duration (MCLT) a lease is granted for the full scope lease duration.

     

    >>While the servers are running in load balanced mode and each of them has leased ip addresses,Could I change the failover relationship to standby mode

    You can switch between hot standby and load balance mode if desired, but you can only use one mode at a time with a single DHCP scope.

     

     

    >>What is the best configuration for MCLT?

    You can configure it as you wish, but we don't recommend making the duration too short.

     

    >>How to prevent the situation of both servers running in partner down state

    If the network connection between DHCP failover partners is broken for an extended period of time and a state switchover interval is configured, it is possible for both DHCP servers to enter the partner down state. In this scenario, both DHCP servers will provide new IP address leases from the entire free IP address pool, resulting in possible IP address conflicts.

    For this reason, it is recommended to increase the state switchover interval.

     

    >>What is the drawback of standby mode and load balanced mode

    In hot standby mode, two servers operate in a failover relationship where an active server is responsible for leasing IP addresses and configuration information to all clients in a scope or subnet. The partner server assumes a standby role, with responsibility to issue leases to DHCP clients only if the active server becomes unavailable.

    Hot standby mode is ideal for scenarios where the failover partner is only intended to be used temporarily when the active server is unavailable.

     

    Load balance mode is the default mode of deployment. In this mode, two DHCP servers simultaneously serve IP addresses and options to clients on a given subnet. DHCP client requests are load balanced and shared between the two DHCP servers.

     

    For your reference:

    DHCP Failover Examples

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

     

    Regards,

    Zoe


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    Tuesday, January 8, 2019 6:03 AM
  • Hi,

     

    Just checking in to see if the information provided was helpful.

    Please let us know if you would like further assistance.

     

    Best Regards,

    Zoe


    Please remember to mark the replies as answers if they help and unmark them if they provide no help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Thursday, January 10, 2019 6:02 AM
  • Hi,

     

    Was your issue resolved?

    If the information provided was helpful, please "mark it as answer" to help other community members find the helpful reply quickly.

    If no, please reply and tell us the current situation in order to provide further help.

     

    Best Regards,

    Zoe


    Please remember to mark the replies as answers if they help and unmark them if they provide no help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Monday, January 14, 2019 2:10 AM
  • Hi,

    As this thread has been quiet for a while, we will propose the solution as answer.

    If you need further help, please feel free to reply this post directly so we will be notified to follow it up. You can also choose to unpropose the answer as you wish.

    BTW, we'd love to hear your feedback about the solution.

    Thanks for your understanding and efforts.

    Best Regards,

    Zoe


    Please remember to mark the replies as answers if they help and unmark them if they provide no help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Wednesday, January 16, 2019 1:59 AM