Mobility Access Points and Controllers
The Mobility Access Points and Controllers domain tests the operational path from an AP booting to a working WLAN: discovery, onboarding, licensing, profiles, and redundancy. Questions often ask what happens next when an AP cannot find its controller or which profile controls a behavior.
AP boot and controller discovery
- An AP boots, obtains an IP address by DHCP, and learns controller addresses through DHCP option 43, DNS resolution of aruba-master, Aruba Discovery Protocol (ADP), or a static controller IP.
- If discovery fails, the AP may fall back to broadcast or remain in an unprovisioned state. Console access and AP LEDs are common troubleshooting aids.
- Controller licensing is per AP; an AP can be connected but unable to serve clients if it is not licensed.
Configuration hierarchy
- ArubaOS uses profiles. Examples: the SSID profile defines the network name and security; the virtual AP profile binds an SSID to a VLAN and AAA profile; the AP group ties virtual APs and radio settings to a set of APs.
- The AAA profile points to authentication servers and derives user roles. A common mistake is editing the SSID profile when the real issue is the virtual AP or AAA profile.
- AP groups are configuration containers, not physical locations. A named AP can belong to one AP group at a time.
Redundancy and scaling
- Controller clusters provide fast failover and coordinated client state. VRRP can provide a virtual IP for management or services.
- Master/local and master redundancy designs in ArubaOS 8 separate management from forwarding.
- Local management allows some controller functions to run on the controller itself when a Mobility Master is unreachable.
Worked example
An AP powers up, gets DHCP, but never appears in the controller's show ap database as Up. You confirm the AP has an IP and can ping the controller. The DHCP scope has option 43 pointing to an old controller address. The AP tries that address, fails, then attempts DNS for aruba-master. Fixing option 43 to the correct controller IP and rebooting the AP lets it discover and onboard. The reasoning: discovery happens before licensing or configuration, so fix reachability and discovery first.
Traps that cost marks
- Assuming an AP that appears in the database is serving clients; check up state and licensing.
- Confusing the SSID profile with the virtual AP or AAA profile.
- Using AP groups as site labels rather than configuration containers.
- Forgetting option 43 format and DHCP scope inheritance.
- Expecting an Instant AP conductor to be a hardware controller.