Dynamic VLAN Pooling
When Dynamic Client VLAN Pooling is enabled on your WLAN, the clients will be assigned IPs from any of the VLANs listed in the pool, which are randomly selected based on MAC hashing algorithm performed by the cloud/AP.
In a single Instant AP cluster, a large number of clients can be assigned to the same VLAN. Using the same VLAN for multiple clients can lead to a high level of broadcasts in the same subnet. To manage the broadcast traffic, you can partition the network into different subnets and use L3-mobility between those subnets when clients roam. However, if a large number of clients need to be in the same subnet, you can configure dynamic client VLAN pooling, in which each client is randomly assigned a VLAN from a pool of VLANs on the same SSID. Thus, VLAN pooling allows automatic partitioning of a single broadcast domain of clients into multiple VLANs.