F5CAB2 BIG-IP Administration Data Plane Concepts (F5CAB2) exam Questions and Answers

Comprehensive and Detailed Explanation From BIG-IP Administration Data Plane Concepts documents:

In BIG-IP LTM, apool member statedirectly affects how traffic is handled at the data plane level. When a pool member ismanually disabled, BIG-IP changes the member’s availability state todisabled, which has specific and predictable traffic-handling consequences.

According to BIG-IP Administration Data Plane Concepts:

Adisabled pool member:

Doesnot accept new connections

Continues to processexisting non-persistent connectionsuntil they naturally close

Isremoved from load-balancing decisions, including persistence lookups

Most importantly for this question:

Persistent connections(such as those created using source-address persistence, cookie persistence, or SSL persistence) arenot honoredfor a disabled pool member

BIG-IP willnot send new persistent trafficto a disabled member, even if persistence records exist

Therefore, when a pool member is manually disabled, itstops processing persistent connections, while allowing existing non-persistent flows to drain gracefully.

Why the Other Options Are Incorrect:

B– Persistent connections are not honored for a disabled pool member

C– Existing connections are not immediately terminated when a pool member is disabled

D– Only the disabled pool member stops accepting new connections, not all pool members

Key Data Plane Concept Reinforced:

Manually disabling a pool member is agraceful administrative actionthat prevents new and persistent traffic from reaching the member while allowing existing connections to complete, which is critical for maintenance and troubleshooting scenarios.

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Comprehensive and Detailed Explanation From BIG-IP Administration Data Plane Concepts documents:

Although remote authentication (LDAP, RADIUS, TACACS+) is acontrol-plane / management-planefeature, it directly affectsavailability and resiliency of administrative access, which is a critical operational HA consideration.

How BIG-IP Remote Authentication Works:

BIG-IP can authenticate administrators against:

LDAP

RADIUS

TACACS+

When remote authentication is enabled, BIG-IPby default relies on the remote serverfor user authentication

If the remote authentication server becomes unreachable, administrators may belocked outunless fallback is configured

Why “Fallback to Local” Is Required:

TheFallback to Localoption allows BIG-IP to:

Attempt authentication against theremote authentication server first

If the remote server isunreachable or unavailable, fall back to:

Local BIG-IP user accounts (admin, or other locally defined users)

This ensures:

Continuous administrative access

Safe recovery during:

Network outages

Authentication server failures

Maintenance windows

This behavior is explicitly recommended as abest practicein BIG-IP administration to avoid loss of management access.

Why the Other Options Are Incorrect:

A. Configure a second remote user directory

Provides redundancyonly 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 maintainadministrative access resiliency, BIG-IP administrators should always enableFallback to Localwhen using remote authentication. This prevents lockouts and ensures access even during authentication infrastructure failures.

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Comprehensive and Detailed Explanation (BIG-IP Administration – Data Plane Concepts):

WithLeast Connections (member), BIG-IP attempts to send new connections to the pool member with the fewest current connections. In a perfectly “stateless” scenario (no affinity), this often trends toward a fairly even distribution over time.

However,persistence overrides load balancing:

When apersistence profileis applied, BIG-IP will continue sending a client (or client group) to thesame pool memberbased on the persistence record (cookie / source address / SSL session ID, etc.).

This means even if another pool member has fewer connections, BIG-IP may still select the persisted member to honor session affinity.

The result can beuneven active connection counts, even though the configured load balancing method is Least Connections.

Why the other options are not the best cause:

A. Priority Group Activation is disabledPriority Group Activation only affects selection when priority groups are configured; disabling it does not inherently create uneven distribution under Least Connections.

B. SSL Profile Server is appliedA server-side SSL profile affects encryption to pool members, but it does not by itself cause skewed selection across pool members. (Skew could happen indirectly if members have different performance/latency, but that’s not the primary, expected exam answer.)

D. Incorrect load balancing methodLeast Connections is a valid method and does not itself explain unevenness unless something is overriding it (like persistence) or pool members are not all eligible.

Conclusion:

Apersistence profileis the most common and expected reason that active connections becomeunevenly distributed, because persistencetakes precedence overthe Least Connections load-balancing decision.

Comprehensive and Detailed Explanation From BIG-IP Administration Data Plane Concepts documents:

This question focuses onconnection behavior when pool members transition from down to up, which is a classic data plane consideration in BIG-IP environments.

What problem is being solved?

When a pool member:

Recovers from a failure

Is enabled after maintenance

Transitions frominactivetoactive

…it can suddenly receive alarge burst of new connections, especially when using load-balancing methods such asLeast Connections. This sudden surge can overload the server.

Why Slow Ramp Time is the correct solution:

Slow Ramp Timeis a pool-level setting that:

Gradually increases the number of connections sent to a newly available pool member

Prevents sudden spikes in traffic

Allows the server to warm up (application cache, JVM, DB connections, etc.)

From BIG-IP Administration Data Plane Concepts:

Slow Ramp Time controls therate at which BIG-IP increases loadto a pool member that has just become available

During the ramp period, BIG-IP artificially increases the member’s connection count, making it appear “busier” and therefore less attractive for new connections

This directly satisfies the requirement toavoid overloading pool members when they become active.

Why the Other Options Are Incorrect:

B. Different Ratio for each member

Ratios controlrelative distributionunder normal operation

They do not prevent a sudden surge when a member becomes active

C. Action On Service Down to Reselect

Controls persistence behavior when a member goes down

Has no impact on connection ramp-up when a member comes back online

D. Same Priority Group to each member

Affects failover logic between priority groups

Does not control connection rate or ramp-up behavior

Key Data Plane Concept Reinforced:

To protect backend servers during recovery events, BIG-IP providesSlow Ramp Time, ensuringgraceful reintroduction of trafficand preventing connection storms that can occur during high-load scenarios.

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Comprehensive and Detailed Explanation (BIG-IP Administration – Data Plane Concepts):

On BIG-IP systems,physical interface bandwidth is fixedby the link speed (for example, 1GbE or 10GbE). When traffic demand exceeds the capacity of a single interface, BIG-IP provideslink aggregationthroughtrunks.

Key concepts involved:

InterfacesA single physical interface (such as 1.1) is limited to its negotiated link speed. You cannot exceed this capacity through software tuning alone.

Trunks (Link Aggregation)Atrunkcombines multiple physical interfaces into a single logical interface.

BIG-IP supports LACP and static trunks.

Traffic is distributed across member interfaces, increasingaggregate bandwidthand providingredundancy.

VLANs are then assigned to thetrunk, not directly to individual interfaces.

Why optionBis correct:

Creating atrunk with two interfacesallows BIG-IP to use both physical links simultaneously.

This increases total available bandwidth (for example, two 10Gb interfaces → up to 20Gb aggregate capacity).

This is thedocumented and supported methodfor scaling bandwidth on BIG-IP.

Why the other options are incorrect:

A. Increase the MTUMTU changes affect packet size and efficiency,not total bandwidth capacity.

C. Assign two interfaces to the VLANBIG-IP doesnotsupport assigning a VLAN to multiple interfaces directly. VLANs must be associated withone interface or one trunk.

D. Set the media speed manuallyMedia speed can only be set up to the physical capability of the interface and connected switch port. It cannot exceed the hardware limit.

Conclusion:

To increase total available bandwidth on BIG-IP when a single interface is insufficient, the administrator must create atrunk object with multiple interfacesand move the VLAN onto the trunk. This aligns directly with BIG-IP data plane design and best practices.