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DHCP adding new scope - the address range and mask conflict with an existing scope

I've taken over a companies network running Windows 2008 R2 Server with the current DHCP address scopes:
172.16.1.71 - 172.16.1.220
Subnet mask: 255.255.0.0

172.20.10.10 - 172.20.10.200
Subnet mask: 255.255.255.0

We're running out of IP addresses in the first scope so I want to add another scope of 172.16.4.10 - 172.16.4.250 but I get the error - "the address range and mask conflict with an existing scope"

DHCP scopes and subnet masks have never been my strong point so can someone help me or point me in the right direction please?

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Dan McFadden

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SOLUTION

Chris

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Dan McFadden

You'd think... but true. Though I doubt that the internal network infrastructure is routing with a 16 bit subnet mask.

Then again, I can always be surprised.

I recommend matching the DHCP scope(s) configuration(s) with that of the active network and subnets configured to be routeable. This includes the subnet masks.

Just saying.

Dan

fruitloopy

ASKER

Had to give points to Chris for the mic drop!

We have 2 domain controllers and only 1 DHCP server so I added a second DHCP server for redundancy, created a new scope on it for the address range we wanted and it's all working fine.

At some point I'll put some time into sorting this out properly