Creating DHCP Scope - Scope Parameters are Incorrect

[newpersn]

Hello,

 

I'm trying to create a few new DHCP scope ready to move away from SWGFL. Currently have 2 vlans running. 

x.x.4.0 / 22

x.x.8.0/ 21

 

When we try and create a new network scope i get a error below - 

I have tired creating both x.x.20.0-x.x.29.255 and x.x.20.0-x.x.39.254

 

(we will be creating a few more ranges as we are adding more vLANs

 

Thanks

Newp

 

 

 

I cant see anything that would be using that scope. 

[TechMonkey]

Do any of your current scopes overlap or are a subset of those new scopes?

What subnet are you using?

[newpersn]

Nope, Cant see it overlapping. 

 

For this range i was trying to use /19 

 

 

[Davit2005]

Online Subnet calculator is your friend 😀

 

Use proper subnet ranges, it helps with routing.

 

https://www.subnet-calculator.com/subnet.php?net_class=B

 

 

Edited June 30, 2025 by Davit2005

[ThomL]

I like the visual subnet tools that let you divide/combine and showing other the other sub/supernets: https://www.davidc.net/sites/default/subnets/subnets.html?network=10.10.0.0&mask=20&division=5.30

Edited June 30, 2025 by ThomL
updated link to match OP's subnets

[newpersn]

Looking at current - I'm not got anything near the range I'm trying to setup. 

 

I cant see anything above range that has been setup. 

 

[Steve21]

From what you said above those do fully clash

x.x.20.0 on a /19 is from

 

x.x.0.1 - x.x.31.254

It won't just go up from the number you've given it, it references a specific range

Steve

Edited June 30, 2025 by Steve21

[ThomL]

The end IP address on the BYOD-VLAN150 isn't at the end of the /21 subnet is that the issue? Should it actually be X.X.15.254?

[newpersn]

Thanks all for help - Not too sure what is going on the with x.x.8.0 network - This was part setup last year but wasn't active but rushed to in action for our BYOD this sept.

 

So glad we got a new core and firewall going in this summer..