172.16.0.1/23 overlaps with 172.16.1.0/24 that is used for "IT-Drift". That is even the literal error message that you've cut off in your screenshot.

You need unambiguous subnets.

And btw: all your broadcast addresses noted in your diagram are incorrect. You might want to check out this excellent Q&A to brush your subnetting.

172.16.0.1/23 overlaps with 172.16.1.0/24 that is used for "IT-Drift". That is even the literal error message that you've cut off in your screenshot.

You need unambiguous subnets.

And btw: all your broadcast addresses noted in your diagram are incorrect. You might want to check out this excellent Q&A to brush up your subnetting skills.

172.16.0.1/23 overlaps with 172.16.1.0/24 that is used for "IT-Drift". That is even the literal error message that you've cut off in your screenshot.

You need unambiguous subnets.

172.16.0.1/23 overlaps with 172.16.1.0/24 that is used for "IT-Drift". That is even the literal error message that you've cut off in your screenshot.

You need unambiguous subnets.

And btw: all your broadcast addresses noted in your diagram are incorrect. You might want to check out this excellent Q&A to brush your subnetting.