Do you currently have them all using one IP subnet in one VLAN and one SSID? What would you be trying to accomplish by having a different IP subnet on each AP/in each classroom?
A couple items which may help:
-- In your situation, a common reason to use different VLANs is to break up the broadcast domain. 25 subnets in one VLAN means a whole lot of broadcast traffic. You'd have less broadcast traffic with one subnet per VLAN.
-- If you have 600 devices which could, theoretically, be connected to each of your subnets at some point or another over the span of a day, then you should use a subnet mask in each subnet allowing enough IP addresses for all your devices. A /23 network has 510 usable IPs, a /22 network has 1022 usable IPs.
-- When an iPad roams to a new AP with the same SSID, it assumes it is on the same subnet and will not request a new IP address. This could cause serious issues with your design.
-- The last point also means that it does no good to have leases more than 1 day, since when the students bring the iPads out of the school and back in, they will always do DHCP discovery upon connecting to a school network. As a practical matter, in modern switched networks, DHCP traffic is barely a blip of bandwidth, so until everything is running well, I advise shorter lease times to give you flexibility to make network changes. Start with an hour, inch it up from there, and no sense going more than 8 hours in any case.
-- A tip from my experience, I rolled out 1,500 iPads in a school with 65 APs, and due to various task, I didn't have time to create different subnets to break up the broadcast domain, but planned to in the first few weeks of school. Conventional wisdom is to never have more than 500 devices in a broadcast domain, but when school started, I found that 1,500 iPads work fine in a single subnet/VLAN. My emergency plan to break up into discrete VLANs and subnets was set aside, I waited until Christmas break to implement it, and even then, the performance improvement was slight. It already worked very well. Despite all the warnings I got, iPads actually are very good with bandwidth, much better than laptops.
Give a little more background on why you want to do this, what are you goals or problems you hope to solve?
Thanks for your quickly answer. I have 125 ipadss, one broadcast domain, one DHCP (Mac Server) one VLAN , one subnet (172.16.X.X/24) one SSID, and one FTTH line outpout (100/10). Everything is working fine.
The problem is that the AP ́s are level 2 layer (no routing). The SWITCH too is level 2. So, I can ́t separate the network in subnet ́s with this SWITCH.
Also, now I have 600 ipad ́s , 4 FTTH lines (100/10) and I need to use them to distribute the load . My first idea was to use the DHCP in the AP ́s. Another idea is to use the 4 FTTH routers like DHCP ́s and the DHCP relay in the AP ́s (I don ́t know if this works in the same broadcast domain). Other people is using a Firewall - load balancing with its own DHCP.
What would you do in my case?
Thanks a lot for your suggestions.
it's a great way to solve the issue of "super-broadcasting" instead super-subnetting :)