I have a scenario with a controller and a separate gateway router connected to the controller's uplink. Configured on this controller is a User VLAN pool. My question relates to the subnet size per User VLAN. I believe that the documentation recommends class C sized subnets. I believe that one key reason for this subnet size is to minimize ARP broadcasts. For example, If my gateway router sends an ARP, the controller can act as an ARP Proxy if it has the IP/MAC information, otherwise it broadcasts the ARP out all its interfaces including the wireless interfaces. Reducing the subnet size reduces the number of ARPs a wireless station will see.
With my 8 co-located controllers, this subnet size leads to hundreds of VLANs! I believe that, in my case, I can increase the subnet size to 512 or even 1024 addresses because of the following:
a) Each controller uses a separate VLAN pool (ie every controller uses different VLAN IDs). Therefore, a controller will not see an ARP that was intended for another controller. This prevents a controller from ARPing while the destination station is associated to another controller. I don't need mobility across controllers.
b) There are no wired stations on the controller for which the controller may not have IP/MAC information.
c) The controller will have IP/MAC information for all associated stations. I don't expect much if any traffic to non associated stations because 99% of the traffic is client/server, initiated by the wireless station.
Based on the above, I would like to increase my subnet size per User VLAN to 512 or even 1024 addresses. I would appreciate any feedback from the forum on this.
Thanks.