User's Manual

575 | Increasing Network Uptime Through
Redundancy and VRRP
Dell Networking W-Series ArubaOS 6.4.x| User Guide
The following section of this document gives an lists requirements and capacity limitations for this feature. For
the procedure to enable the extended standby controller capacity, see Configuring High Availability on page
576,
Starting with ArubaOS 6.4.0.0, a W-7200 Seriescontroller acting as a standby controller can oversubscribe to
standby APs by up to four times that controller's rated AP capacity, and a standby W-6000M3controller
module or W-3600controller can oversubscribe by up to two times its rated AP capacity, as long as the tunnels
consumed the standby APs do not exceed the maximum tunnel capacity for that standby controller.
Feature Requirements
This feature can be enabled on controllers in a master-local topology where centralized licensing is enabled on
the active and standby controllers, or on independent master controllers that are not using VRRP-based
redundancy. If centralized licensing is disabled, the standby AP oversubscription feature are disabled also.
Standby controller oversubscription and the high availability state synchronization features are mutually
incompatible cannot be be enabled simultaneously. If your deployment uses the state synchronization feature,
you must disable it before you enable standby controller oversubscription.
W-3200, W-3400 and W-600 Seriescontrollers do not support this feature.
Standby Controller Capacity
The following table describes the AP oversubscription capacity maximum supported tunnels and for controllers
that support this feature.
Controller Model
Standby AP
Capacity
Maximum Tunnels Sup-
ported
W-6000M3 2x rated APcapacity 16384 tunnels
W-3600 2x rated APcapacity 16384 tunnels
W-7210 4x rated APcapacity 16384 tunnels
W-7220 4x rated APcapacity 32768 tunnels
W-7240 4x rated APcapacity 65536 tunnels
Table 105: Controller Support for Standby Oversubscription
To determine the number of standby tunnels consumed by APs on each active controller, multiply the number
of APs on the active controllers by the number of BSSIDs per AP. As an example, consider a deployment with
four active W-7210controllers that each have 512 APs with 8 BSSIDs. The APs on each active controller
consume (512 * 8) tunnels, for a combined total of 16,384 tunnels. A single W-7210controller using the
standby controller oversubscription feature can act as the standby controller for all four active controllers in
this example, because this topology is within the 4x rated AP capacity limit and maximum tunnel limit for the
W-7210controller model.
If the network administrator later changed all the APs in this deployment to support 10 BSSIDs, each active
controller would use (512 * 10) tunnels, for a combined total of 20,480 tunnels on the four active controllers.
The tunnels required by the APs on the active controllers would then exceed the maximum tunnel limit for the
standby controller, so the standby controller can no longer support all APs on the active controllers. Dynamic
changes to configuration (such as the addition of BSSIDs to any AP group) causes all the standby APs to
disconnect and reconnect back to the standby controller defined by their updated configuration