Support for Aruba WLC and Fault Tolerance

In a large campus WLAN that has separate network services and aggregation layers, APs and AMs should never terminate on the master controller. APs and AMs should terminate only on the local controller. Aruba Mobility Controllers are deployed in clusters that consist of a master and one or more local controllers to solve this management scalability issue. This design is the recommended model when two or more controllers exist in the same network. This design is depicted in the Aruba Mobility Controllers and Deployment Models Validated Reference Design.
casp1032
In a large campus WLAN that has separate network services and aggregation layers, APs and AMs should never terminate on the master controller. APs and AMs should terminate only on the local controller. Aruba Mobility Controllers are deployed in clusters that consist of a master and one or more local controllers to solve this management scalability issue. This design is the recommended model when two or more controllers exist in the same network. This design is depicted in the Aruba Mobility Controllers and Deployment Models Validated Reference Design.
 Large scale deployments generally involve more than two controllers. When you have more than a single pair of controllers, change control and network consistency can become an issue. In an Aruba network that uses a master/local design, configuration is performed only on the master and it is pushed down to the locals. Local controllers reside at the aggregation layer of the Aruba overlay architecture. They handle AP termination, user authentication, and policy enforcement. When you configure any local controller, you must know the IP address of the master and the pre-shared key (PSK) that was used to encrypt communication between the controllers. The control channel between all Aruba controllers is protected by an IP Security (IPsec) connection.
 Note: The controllers have a preconfigured key at first boot. Change this key after the first boot so that the operation of the master/local cluster is secure.
 For more details on the functions and responsibilities of master and local mobility controllers in Aruba architecture, see the Aruba Mobility Controllers and Deployment Models Validated Reference Design.
Fault Tolerance in Aruba WLC
Large network would have a master/backup master pair and a lot of local controllers that point to them.  If the master controller has a problem, the backup master would step in, and you would still have an appliance that has read-write capability in your network without any interruption.
If you have a master/local, but no backup master, you would lose the ability to make global changes to your network.  Your network would however, still be able to run. 
With this configuration, if the master becomes unreachable or unavailable and no standby master has been configured, the network continues to operate as expected, except for certain operations. You cannot perform configuration, RF visualization, or location services until connection to the master controller is restored. The master controller is needed to perform configuration and reporting, but it is not a single point of failure in the network.
The master is where all configuration changes are made.  The local connects to the master and gets the majority of its configuration from it.  Selecting "Standalone" during the startup wizard just allows you to avoid configuring credentials for a local to connect to it.  A "Standalone" controller is essentially a master. All controllers, whether Master or Local, can terminate access points.A backup master is a master controller that you cannot terminate access points on.  It's sole responsibility is to back up the only read-write appliance you have in your network. A master does a lot of the database processing, so in larger environments, you don't want access points to terminate at all.
Controller Management
CA Spectrum allows you automatically detect the Role change (Master to Backup, Master to Local , Local to Master, etc all combinations).
This supports the '
wlsxNSwitchRoleChange'
trap and poll based Association changes in WLC Manager Topology. AP's should automatically moved based on the role change(s) occurred between Master and Local controllers, after every device polling interval.You should be able to see the role changes for the configured
Role Change Interval Period
, which is 24 hours by default.However, the next scheduled polling interval is user configurable.
  1. Select the
    Aruba
    vendor folder in the OneClick Explorer, navigate to the
    Component detail: Aruba of type WLCVendor
    and select the
    Information
    tab.
  2. Expand 
    Controller Managemen t
    .
    Aruba Controller management.png
     
  3. Use the
    Update Now
    button, for the following scenarios:
    • View changes made at Controller level to roles (master and local) and the resultant change in hierarchy
    • If Traps are disabled so switchover (role change) information and hierarchy mapping is not reflecting or happening
    • You have made changes to the hierarchy and wants the changes to reflect before the next scheduled polling interval. 
  4. Click
    set
    and configure your desired Controller Role Change Interval in hours.