Environment : This article applies to all IAP platforms and OS versions.
1) How do the IAP devices communicate with each other? (which protocol, encryption, tunnel)
Inter-AP communication for management is done through PAPI. (Port 8211 just as campus AP to controller.)
2) How do the devices sync with each other and with the controller? (which protocol, channel, tunnel, encryption, sync time and interval)
All Aruba Instant APs must be on a Layer 2 VLAN to be part of the same virtual controller group. The master virtual controller is selected based on master election protocol. If master virtual controller goes down, then the AP with most uptime is next eligible. Inter-AP communication for management is done through PAPI. The virtual controller is discovered using a Layer 2 multicast protocol that is very efficient. In a stable state, it results in only one small packet sent every second.
3) When the client is logged into the virtual controller and that controller goes off, the link breaks and the client does not connect to another virtual controller. Why? I thought that failover is supported?
If the primary virtual controller fails, another Aruba Instant AP automatically takes on the role with no disruption. The primary virtual controller functions like any other Aruba Instant with full RF scalability. We know that another IAP takes over as the primary virtual controller, however access INTO the virtual controller is disrupted momentarily. Please try again.
When the current virtual controller fails, system elects a new virtual controller. The election process gives preference to AP with the largest uptime if there is a conflict. The Instant virtual controller sends beacons every second to notify that it is active. New APs use this beacon to discover the virtual controller as well. When the beacon stops, all APs go to the elect virtual controller state where they try to elect a new virtual controller.
The new virtual controller sends gratuitous ARP to update upstream devices.
4) What kind of support does Aruba Instant have for client roaming? Is there any difference between the "normal" Aruba and Aruba Instant? (issues, performance)
We do have the same ARM algorithm as usual. ARM ensures low-latency roaming, consistently high performance, and maximum client compatibility in a multichannel environment. ARM ensures the fair distribution of available Wi-Fi bandwidth to mobile devices. By doing so, ARM ensures that data, voice, and video applications have sufficient network resources at all times. ARM allows mixed 802.11a, b, g, and n client types to interoperate at the highest performance levels. IAP also acts as a node to coordinate DHCP address allocation for network address translated clients, which ensures mobility of the clients when they roam between different IAPs.