Issues Recreating DHCP Scope

Well, backing up a bit...

The original DHCP scope has a 23 bit mask, so valid IPs would 192.168.10.1 - 192.168.11.254.  So, that's 192.168.10.0/23.

You said 192.168.10.1-255 were used for fixed IPs and 192.168.11.1-254 are used for dynamic addresses.

Were you using reservations for the fixed IPs?

Regarding the Cisco switches, and everything else on your network, changing that subnet mask from /23 to /24 means you just told the whole network that 192.168.10.x and 192.168.11.x are on two separate networks and that means you have to have a router to route between them.

Are those layer 3 switches?

Yes,  The person who initially set this up defined it with a netmask of /23 but only assigned IP addresses in the 192.168.11.0/24 subnet.   He was able to set an IP range of 192.168.11.0-192.168.11.255 I have been requested to break it up into two seperate vlans.  

On the switch the original VLAN was setup as /23 to match the DHCP scope.   I tried setting up two vlans.  One for 192.168.10.0/24 with a fixed ip address and one for 192.168.11.0/24 with a fixed IP address as well so they would route between each other.  I added a Helper address to the 192.168.11.0 VLAN to route the DHCP request but it did not make any difference.  .

Joseph Hornsey has already given good advice.

What's important is that you keep your subnets as you want them / need then.  Then the DHCP should follow that.  "The tail shall not wag the dog".

Then, you set up DHCP in a manner that's consistent with your subnet and plan for using IP addresses.

In this case I would suggest keeping the old subnet of /23.  That has nothing much to do with DHCP as it will follow.
Then, you choose a range within  192.168.10.1 - 192.168.11.254 to serve with DHCP.
There are dynamic assignements and there can be static assignments both handled by DHCP.
And, there will likely be static IP addresses manually entered in their respective devices.

I'm used to the static assignments from DHCP being outside the DHCP "scope" of dynamic addresses or the "dynamic address pool".

Just to be clear, you cannot have " DHCP scope of 192.168.11.0/23 with an address range of 192.168.11.0-192.168.11.255" at least not in my English.  I would rather say this:
you have a subnet of 192.168.10.0/23 and a DHCP scope (or dynamic pool) of 192.168.11.0 to 192.168.11.254.

I would recommend getting back to the original settings (in your head at least if not in the system).
Then I would consider the objective more carefully.

If the objective is to set the dynamic pool for DHCP from 192.168.11.0-192.168.11.254 then do that but keep the subnet mask at /23.

But beware of:
- Any static assignments via DHCP for anything in 192.168.10.1-192.168.10.255?
- Any static IP addresses assigned in 192.168.11.0 - 192.168.11.254 that will interfere/conflict with the DHCP pool?

Basically it is currently working and I see no need to change it.  However our corporate office sees things differently and I have been asked to change it.  They want the Fixed IPs and the Dynamic IPs on separate VLANS with DHCP configured to match.

( Just to be clear, you cannot have " DHCP scope of 192.168.11.0/23 with an address range of 192.168.11.0-192.168.11.255" at least not in my English.)  

 I am just reporting what is in the DHCP settings.   It is setup with a netmask of 255.255.254.0 and the IP range according to the DHCP settings is 192.168.11.0-192.168.11.255.  I don't know how he got it in there but that is what it is currently set to.  

The end goal is to have the statically assigned IP addresses on a separate VLAN from the Dynamically assigned IP addresses.   I thought I handled that by creating the two VLANS on the switch and adding the DHCP helper address.   I have add some VLANs for special equipment/ports and I have set them up the same way using the same server for DHCP with no problems.

If that's the case, then here's what you have to do:

1. Create a VLAN for 192.168.10.0/24.
2. Create a VLAN for 192.168.11.0/24.
3. Put a router in there.

A VLAN is simply a logical grouping of switch ports which the switch treats as two completely separate and different networks.

Switches are layer 2 devices, and they do not route traffic between the subnets.

If it's a layer 3 switch, than it can route traffic between subnets (which might be the case given your comment regarding having VLANs for special equipment/ports).  In this case you are going to have to configure the switch to do so.

Remember, up until this point, your switch believed everything from 192.168.10.1-192.168.11.254 were in the same network because that's what the subnet mask told it.  Now, you're telling it that there are two different networks.  So, you're going to have to tell it to route that traffic.

The switches are configured for Layer 3 routing.   I created both VLANs with routing between them.    I have done the same thing for multiple VLANs but this time I can not get an IP address afterwards.  

I was hoping I had missed something obvious.

Did you check are default gateways properly configured (in the proper IP range and proper IP address (beside IP helper addresses on SVIs)?

And this one:   - IP Telephony????
You have issues with phones getting IP address?

Thanks for the suggestions and comments.   I was able to use a fixed IP address to communicate with everything  I am pretty sure I used the correct gateway and helper addresses but I have backed out everything out so I can't verify it at this time.  

I am going to close this ticket since it will probably be a couple of weeks before I can get the network to myself again to redo the changes.

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Thanks for giving me the points.  When you decide to get back into this, find me on here and I'll be more than happy to help!