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For simplicity sake, let's assume I'm trying to split my DHCP scope into two halves. On one of the halves I want to use MAC address filtering. I'm essentially trying to get a certain type of device with a known Mac address to have contiguous IP addresses. The problem is since the subnet is the same, windows server complains.

The subnet is 10.0.0.0/24. I'm trying to allocate 10.0.0.21-10.0.0.127 for default devices and 10.0.0.128-10.0.0.254 for devices with a MAC address of 11-AA-BB-*. The problem is they all use 10.0.0.1 for the default gateway and have 10.0.0.0/24 as their subnet

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    Why would you need to split the scope? Just limit the pool and set reservations for the devices that need them. In fact, when you create the reservations, it should create a pool exclusion automatically. – GregL Oct 9 '15 at 18:29
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    @GregL I can not create reservations based on a wildcard MAC address. I want to say anything with 01-AA-BB-* get a group of IP addresses in the upper half of the range while everyone else gets the lower half. – john anderson Oct 9 '15 at 18:33
  • Why not make two at /25? – Kevin Roberts Oct 9 '15 at 18:38
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    If I properly understand the MAC filtering abilities of the Windows DHCP service, it's set at the server-level. This would mean having two DHCP servers on the same segment, each serving up IPs to either the "default devices" or the others. – GregL Oct 9 '15 at 18:42
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    @KevinRoberts, yes but the host will probabally not like that. A host can't be assigned 10.0.0.150/25 and have a default gateway of 10.0.0.1 – john anderson Oct 9 '15 at 19:00
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The question doesn't specify a specific DHCP server to use, so I'm going to be a little cheeky, and offer up an alternative to Microsoft DHCP, which, judging from the comments and from looking around a little myself doesn't seem to be able to do what you want.

From a cursory reading of the manual page for ISC dhcpd (the Internet Systems Consortium DHCP Server), it would appear that this server has the configurability you're after to do this - specifically see the example under the "Subclasses" section. The example won't work as-is, but it demonstrates that the server has the configurability neccessary to do what you want.

Unfortunately, it doesn't run on Windows directly, although you can install for example a Linux virtual machine using Hyper-V on a Windows Server in order to run this on existing hardware.

Another alternative is simply to split the special devices off on a different VLAN. If you have managed switches, many models can automatically assign ports to VLANs depending on the MAC addresses of the clients. This feature may be called "Voice VLAN" on some models. This would of course not meet the "same subnet" requirement of your question, but you can always just get routing going between the two subnets.

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