Although remote authentication (LDAP, RADIUS, TACACS+) is a control-plane / management-plane feature, it directly affects availability and resiliency of administrative access , which is a critical operational HA consideration.
How BIG-IP Remote Authentication Works:
BIG-IP can authenticate administrators against:
When remote authentication is enabled, BIG-IP by default relies on the remote server for user authentication
If the remote authentication server becomes unreachable, administrators may be locked out unless fallback is configured
Why “Fallback to Local” Is Required:
The Fallback to Local option allows BIG-IP to:
Attempt authentication against the remote authentication server first
If the remote server is unreachable or unavailable , fall back to:
Local BIG-IP user accounts (admin, or other locally defined users)
This ensures:
Continuous administrative access
Safe recovery during:
This behavior is explicitly recommended as a best practice in BIG-IP administration to avoid loss of management access.
Why the Other Options Are Incorrect:
A. Configure a second remote user directory
Provides redundancy only if both directories are reachable
Does not help if remote authentication as a whole is unavailable
B. Configure a remote role group
Maps remote users to BIG-IP roles
Does not affect authentication availability
D. Set partition access to “All”
Controls authorization scope after login
Has no impact on authentication success
Key Availability Concept Reinforced:
To maintain administrative access resiliency , BIG-IP administrators should always enable Fallback to Local when using remote authentication. This prevents lockouts and ensures access even during authentication infrastructure failures.
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