The IPAM DHCP Split Scope Wizard

Split scopes are used to for several reasons, either to perform load balancing between two DHCP servers, or to ensure high availability DHCP services for your network.

When you split a scope, the primary server is responsible for a certain group of IP addresses, and the secondary is responsible for the remainder. An offer delay (generally between 1000 and 5000 milliseconds) is set for the secondary server to ensure that if the primary server is unable to provide an IP address within the offer delay time, the secondary server will do so using its pool of addresses.

Scopes are usually split into one of two configurations:

  • 50/50, where half of the IP addresses are on the primary DHCP server and half are on the secondary server. This configuration is usually used for load balancing.
  • 80/20, where 80% of the IP addresses are on the primary DHCP server and only 20% are on the secondary server. This configuration is generally to ensure high availability.

 

You start with a scope01 on your primary DHCP server. Scope01 includes the entire subnet of 10.10.10.0/24 (254 IP addresses), with no exclusions. You split scope01, and name the second scope scope02 on your secondary DHCP server. You choose an 80/20 split.

Now, scope01 will still span the entire subnet, but will exclude the last 20% of the addresses in that subnet (10.10.10.204-254). Scope02 will also span the entire subnet, but will exclude the first 80% of the addresses in that subnet (10.10.10.1-203).

IPAM 3.1 now includes a Split Scope wizard that minimizes the guesswork.

Here is a quick summary of how the wizard works.

Using the DHCP Split Scope Wizard:

To open the split scope wizard, click the DHCP & DNS Management tab >> DHCP Scopes >> select a DHCP scope to be split >> click Split Scope.

Note: To perform the DHCP split scope operation, ensure you have two DHCP servers added to the IPAM.

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Defining Split Scope» The split scope wizard shows you the source DHCP server selected for the split scope operation, and allows you to select the target DHCP server to where the scope and its IP addresses need to be split.

Define the Source & Target DHCP Servers for Performing Split Scope Operations.

definescope.png


Range Distribution» This step allows you to specify the percentage of IP addresses to allocate to the source and target DHCP scope servers.» You can just drag the percentage scale to set the split percentage as required. The IP addresses within the DHCP scopes will be changed accordingly to reflect the percentage split.» Or, if you have specific IP address ranges decided for both the servers, you can just enter them in the Include IP Addresses & Exclude IP Addresses text fields, and the percentage scale will be adjusted accordingly.

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Once range distribution is complete, click Finish, and you will get a pop-up window confirming the successful split scope operation.


Looking Up the IP Address Split (After Performing the DHCP Split Scope Operation)» You can now go to the DHCP Servers tab and do a mouse-over on both the source and target DHCP servers and see the IP address range according to the split Looking up the IP Addresses on the DHCP Servers after the Split Scope Operation


For a more detailed steps walkthrough see: How To Perform DHCP Split Scope using SolarWinds IP Address Manager

For more info on all the new features in IP Address Manager 3.1 see:

IP Address Manager – IPAM Software from SolarWinds