DHCP “The specified range either overlaps an existing range or is not valid”.

Problem

I found an interesting issue when trying to adjust DHCP Scopes to a new range causing the error:

“The specified range either overlaps an existing range or is not valid”.

Even though the range is valid.

For example changing:

192.168.1.121 to 192.168.1.130

TO

192.168.1.151 to 192.168.1.160

Will result in the above error.

Cause

On Microsoft DHCP you are not permitted to shift ranges along which is why the error message appears.

The above scenario falls in the category of “Not Alowed: Shifting to left”.

Source: https://support.microsoft.com/kb/2634442/en-gb?wa=wsignin1.0

Resolution

1. Modify the Start IP to include the whole range, and modify the end IP to the end of your required range.

i.e.

192.168.1.1 to 192.168.1.160

This should be allowed as it is regarded as “expanding your scope”

2. Modify the Start IP to the correct value

192.168.1.151 to 192.168.1.160

The change should not apply as it is regarded as “shrinking your scope”.