Hi, so let's answer your questions...
1)I have around 800+ access points, and 2 identify controllers. I have all ap's and 2 controllers in same vlan.Will there be any issue.
A: Yes, a lot of broadcasts.
2) If i want to create 4 subnets for 800+ access points and seperate the ap and controller subnet, how can i achieve it, do i need toplogies?
A: In reference to 1) I hope that the subnets are also in a different VLAN.
Create 4xAP VLANs in the switch network and 1x VLAN for the controller and the L3 core switch should route between the subnets.
Yes, you always need a topology.
3) We also have 4000 end users in a single subnet, i know its a lot, but i want to split them into 12 subnets, how can i achieve this, what kind of topolgies i need to have.
A: as per 4) you want bridge@AP - you'd do that with i.e. NAC or RADIUS.
Just put the users in a different role (VLAN) that the NAC/RADIUS provide to the controller.
4)I want to bridge traffic locally at AP itself and use only one port say esa1 which will be the management port ......
A: no problem to do that
But why not get some local/remote help from a Extreme Partner for 1-2 days as 800APs is not what I call a small network.....
-Ron