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Dhcp "Failover" vs Dhcp "Split-Scope" vs Failover Cluster "DHCP Server" Role RRS feed

  • Question

  • Afternoon,

    When it come to HA of DHCP, there are at least 3 options there:

    • *DHCP Failover
    • *DHCP Split Scopes
    • *Microsoft Failover Cluster DHCP Server role

    Split-scope vs failover vs clustered dhcp

    In what instances anybody would go for clustered "DHCP Server" in comparison with 2 remaining technologies???

    Friday, October 18, 2019 5:32 PM

All replies

  • Hi ,

    In previous OS version, there are only two high availability options for DHCP:

    1.DHCP in a Windows failover cluster.

    2.Split scope DHCP. 

    DHCP failover is a new high availability option in server 2012 and later OS.

    The clustering deployment option uses a single shared storage. This makes the storage a single point of failure, and requires additional investment in redundancy for storage. In addition, clustering involves relatively complex setup and maintenance. 

    DHCP failover is an improvement on the DHCP in a Windows failover cluster.

    Here is an similar thread discussed before, you could have a look:

    Difference between DHCP function within Failover Cluster and DHCP failover ?

    For more details about DHCP high availability options, please refer to the following link:

    DHCP high availability options

    Best Regards,

    Candy


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    Monday, October 21, 2019 3:21 AM
  • Yet, in Cluster Server Manager you have the ability to cluster DHCP server. I understand that preferable way is DHCP Failover in DHCP, but why do they cluster DHCP Servers? Does this mean you use it only in pre-2012 WS and DHCP Failover is used in 2012+ WS?
    Monday, October 21, 2019 6:08 PM
  • Hi,

    There were some differences in pre-Windows Server 2012 versions, you'll find them over here:
    Step-by-Step: Configure DHCP for Failover

    Quoting from the above link:

    DHCP failover overview
    In Windows Server® 2008 R2, there are two high availability options available for DHCP Server deployment. Each of these options is associated with some challenges.

    1. DHCP in a Windows failover cluster. This option places the DHCP server in a cluster with an additional server configured with the DHCP service that assumes the load if the primary DHCP server fails. The clustering deployment option uses a single shared storage. This makes the storage a single point of failure, and requires additional investment in redundancy for storage. In addition, clustering involves relatively complex setup and maintenance.

    2. Split scope DHCP. Split scope DHCP uses two independent DHCP servers that share responsibility for a scope. Typically 70% of the addresses in the scope are assigned to the primary server and the remaining 30% are assigned to the backup server. If clients cannot reach the primary server then they can get an IP configuration from the secondary server. Split scope deployment does not provide IP address continuity and is unusable in scenarios where the scope is already running at high utilization of address space, which is very common with Internet Protocol version 4 (IPv4).

    DHCP failover in Windows Server 2012 enables administrators to deploy a highly resilient DHCP service to support a large enterprise without the challenges of the options discussed earlier. The main goals of the feature are the following:

    • Provide DHCP service availability at all times on the enterprise network.

    • If a DHCP server is no longer reachable, the DHCP client is able to extend the lease on its current IP address by contacting another DHCP server on the enterprise network.

    The DHCP server failover feature provides the ability to have two DHCP servers provide IP addresses and option configuration to the same subnet or scope, providing for continuous availability of DHCP service to clients. The two DHCP servers replicate lease information between them, allowing one server to assume responsibility for servicing of clients for the entire subnet when the other server is unavailable. It is also possible to configure failover in a load-balancing configuration with client requests distributed between the two servers in a failover relationship.

    DHCP failover in Windows Server 2012 provides support for a maximum of two DHCP servers, and the failover relationship is limited to IPv4 scopes and subnets. Network nodes using Internet Protocol version 6 (IPv6) typically determine their own IPv6 address using stateless IP auto configuration. In this mode, the DHCP server delivers only the DHCP option configuration, and the server does not maintain any lease state information. A high availability deployment for stateless DHCPv6 is possible by simply setting up two servers with identical option configuration. Even in a stateful DHCPv6 deployment, the scopes do not run under high address utilization, which makes split scope a viable solution for high availability.


    Best regards,
    Leon


    Blog: https://thesystemcenterblog.com LinkedIn:

    Monday, October 21, 2019 6:23 PM
  • Hi ,

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

    Please let us know if you would like further assistance.

    Best Regards,

    Candy


    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, October 23, 2019 8:04 AM
  • Hi ,

    You could mark the useful reply as answer if you want to end this thread up.

    If there is anything else we can do for you, please feel free to post in the forum.

    Best Regards,

    Candy


    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, October 25, 2019 5:59 AM