What is Split scope ? And its use in DHCP ?

Server 2008 R2 provides an easy way to split DHCP scopes per best practices. Best practices normally dictate allocating 80 percent of the address scope to the primary DHCP server and 20 percent to a second DHCP server which, which would be configured with a delay in responding to address lease requests. With this configuration, clients will usually get an address from the primary DHCP server.

To use the split scope, first create the DHCP scope as normal and then select Split-Scope from the Advanced menu of the scope, as shown below.

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The Split-Scope wizard will launch. Click Next to go to the main screen, which allows you to select the second DHCP server that will take over a portion of the scope, as shown here.

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You can now configure which IP addresses to allocate to the second DHCP server, either by adjusting the percentages or by directly setting the IP addresses. Click Next once set.