F5CAB2 Exam Dumps - F5-CA Questions and Answers

For BIG-IP to send or receive traffic on a VLAN, that VLAN must be bound to a physical interface or a trunk. Creating a VLAN object and a Self IP alone is not sufficient to establish data-plane connectivity.

From the exhibit:

The VLAN (vlan_1033) exists and has a tag defined.

A Self IP is configured and associated with the VLAN.

However, traffic cannot reach servers on that VLAN.

This indicates a Layer 2 connectivity issue, not a Layer 3 or HA issue.

Why assigning a physical interface fixes the problem:

BIG-IP VLANs do not carry traffic unless they are explicitly attached to:

A physical interface (e.g., 1.1), or

A trunk

Without an interface assignment, the VLAN is effectively isolated and cannot transmit or receive frames, making servers unreachable regardless of correct IP addressing.

Why the other options are incorrect:

A. Set Port Lockdown to Allow AllPort Lockdown controls which services can be accessed on the Self IP (management-plane access), not whether BIG-IP can reach servers on that VLAN.

B. Change Auto Last Hop to enabledAuto Last Hop affects return traffic routing for asymmetric paths. It does not fix missing Layer 2 connectivity.

D. Create a Floating Self IP addressFloating Self IPs are used for HA failover. They do not resolve reachability issues on a single device when the VLAN itself is not connected to an interface.

Conclusion:

The servers are unreachable because the VLAN has no physical interface assigned. To restore connectivity, the BIG-IP Administrator must assign a physical interface (or trunk) to the VLAN, enabling Layer 2 traffic flow.

The BIG-IP system uses a specific precedence algorithm to determine which virtual server (listener) should process an incoming packet when multiple virtual servers might match the criteria. Since BIG-IP version 11.3.0, the system evaluates three primary factors in a fixed order of importance:

Destination Address: The system first looks for the most specific destination match. A "Host" address (mask /32) is preferred over a "Network" address (mask /24, /16, etc.), which is preferred over a "Wildcard" (0.0.0.0/0).

Source Address: If multiple virtual servers have identical destination masks, the system then evaluates the source address criteria. Again, a specific source host match is preferred over a source network or a wildcard source.

Service Port: Finally, if both destination and source specifications are equal, the system checks the port. A specific port match (e.g., 80) is preferred over a wildcard port (e.g., or 0).

Following this logic, a virtual server configured with a specific destination host, a specific source host, and a specific service port represents the highest level of specificity and thus the highest preference.

To meet the requirement of fault tolerance when one interface goes down, BIG-IP must use link aggregation so that loss of a single physical link does not isolate the VLAN(s).

How the objects relate (data plane view)

Interfaces = physical links.

Trunk (LACP) = bundles multiple interfaces into one logical link that provides redundancy (and possibly bandwidth aggregation).

VLANs are assigned to interfaces or trunks. If you need multiple VLANs on the same trunk, they must use 802.1Q tagging (because you can only have one untagged VLAN per interface/trunk).

Self IPs are then placed on the VLANs to provide BIG-IP presence and routing/ARP functions, but self IPs are not what provides link resiliency—the trunk does.

Why Option D is correct

You have two physical interfaces and you want resiliency if one fails → put both interfaces into one trunk with LACP enabled.

You need both external and internal VLANs on those same two links → both VLANs should be configured as tagged on that trunk, so they can coexist on the same aggregated link.

If either physical interface fails, the trunk remains up via the remaining interface, keeping both VLANs operational.

Why the other options are incorrect

A: Two VLANs cannot both be untagged on the same trunk/interface. Only one untagged VLAN is possible; additional VLANs must be tagged.

B: Two trunks “each with one VLAN” would typically mean splitting VLANs across separate trunks. With only two interfaces total, that becomes one interface per trunk—if one interface goes down, the VLAN on that interface is down (no redundancy for that VLAN).

C: Same redundancy problem as B, and disabling LACP removes the negotiated aggregation behavior expected when the switch engineer specifically requested LACP.

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In the BIG-IP system object hierarchy, health monitors can be applied at three levels: Node, Pool, and Pool Member.

Pool Level (Properties): Applying a monitor at the Pool > Properties level is the most common and efficient administrative practice. When applied here, the monitor is inherited by all members of that pool. If the monitor fails for a specific member, that member is marked "down" specifically for that pool.

Node Level: If a monitor is applied at the Node level (Local Traffic > Nodes), it checks the health of the physical IP address itself. If it fails, that node (and all pool members associated with it) is marked down globally across the entire system.

Member Level: Applying a monitor at the Pool > Members level allows for specific "per-member" monitoring, which is usually only done if different members in the same pool require different health checks.

The Specific Case: For a standard database pool like DB_Pool, the administrator should navigate to Local Traffic > Pools > DB_Pool > Properties and select the appropriate monitor (e.g., a custom TCP or Oracle monitor) from the "Health Monitors" configuration section.

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:

LDAP

RADIUS

TACACS+

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:

Network outages

Authentication server failures

Maintenance windows

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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In an Active/Standby BIG-IP design, application availability during failover depends on both units having equivalent data-plane connectivity for the networks that carry application traffic. Specifically:

VLANs are bound to specific interfaces (and optionally VLAN tags).

Floating self IPs / traffic groups move to the new Active device during failover.

For traffic to continue flowing after failover, the new Active device must have the same VLANs available on the correct interfaces that connect to the upstream/downstream networks.

What the symptom tells you:

Traffic works when Device A is Active

Traffic fails when Device B becomes Active

Failback immediately restores traffic

This pattern strongly indicates the Standby unit does not have the VLAN connected the same way (wrong physical interface assignment), so when it becomes Active, it owns the floating addresses but cannot actually pass traffic on the correct network segment.

Why Interface mismatch is the best match:

If the Active unit is already working, its interface mapping is correct.

The fix is to make the Standby unit’s VLAN/interface assignment match the Active unit.

That corresponds to changing the Standby device interface to 1.1.

Why the Tag options are less likely here (given the choices and the exhibit intent):

Tag issues can also break failover traffic, but the question/options are clearly driving toward the classic HA requirement: consistent VLAN-to-interface mapping on both devices so the data plane remains functional after the traffic group moves.

Conclusion: To avoid an outage on the next failover, the BIG-IP Administrator must ensure the Standby device uses the same interface (1.1) for the relevant VLAN(s) that carry the application traffic, so when it becomes Active it can forward/receive traffic normally.

In BIG-IP high availability (HA) configurations, MAC Masquerade is used to speed up failover by allowing traffic-group-associated Self IPs to retain the same MAC address when moving between devices. This prevents upstream switches and routers from having to relearn ARP entries during a failover event, resulting in near-instant traffic recovery.

By default, MAC masquerade applies one MAC address per traffic group, regardless of how many VLANs the traffic group spans. This can create problems in some network designs because the same MAC address appearing on multiple VLANs may violate network policies or confuse switching infrastructure.

To address this, BIG-IP provides Per-VLAN MAC Masquerade, enabled by the database variable:

`tm.macmasqaddr_per_vlan = true`

When this feature is enabled:

BIG-IP derives a unique MAC address per VLAN

The base MAC address configured on the traffic group remains the first four octets

The last two octets are replaced with the VLAN ID expressed in hexadecimal

The VLAN ID is encoded in network byte order (high byte first, low byte second)

### VLAN ID Conversion:

VLAN ID: 1501 (decimal)

Convert to hexadecimal:

1501₁₀ = 0x05DD

High byte: 05

Low byte: DD

### Resulting MAC Address:

Base MAC: `02:12:34:56:00:00`

Per-VLAN substitution → last two bytes = `05:DD`

Final MAC address:

`02:12:34:56:05:dd`

### Why the Other Options Are Incorrect:

A (01:15) – Incorrect hexadecimal conversion of 1501

B (dd:05) – Byte order reversed (little-endian, not used by BIG-IP)

D (15:01) – Uses decimal values instead of hexadecimal

### Key BIG-IP HA Concept Reinforced:

Per-VLAN MAC Masquerade ensures Layer 2 uniqueness per VLAN while preserving the fast failover benefits of traffic groups, making it the recommended best practice in multi-VLAN HA deployments.

BIG-IP virtual server types define how traffic is handled at the data plane when it matches a virtual server’s destination address and service port.

According to BIG-IP Administration Data Plane Concepts:

Standard virtual server

The default and most commonly used type

Accepts client connections and forwards traffic to pool members

Supports both TCP and UDP traffic

Allows full use of profiles (UDP, FastL4, persistence, etc.) and iRules

Required when the goal is to process and pass traffic through BIG-IP

Drop virtual server

Silently discards matching traffic

No response is sent to the client

Reject virtual server

Actively rejects traffic by sending an error response

For UDP, BIG-IP may send an ICMP unreachable message

Block virtual server

Used to block traffic at the virtual server level

Traffic is neither forwarded nor processed by pools

In this scenario:

The administrator explicitly wants the UDP traffic to be forwarded

Only a Standard virtual server forwards traffic to a pool or next-hop destination

Why the Other Options Are Incorrect:

A. Drop – Traffic is silently discarded

B. Reject – Traffic is actively rejected

C. Block – Traffic is blocked and not forwarded

Key Data Plane Concept Reinforced:

When traffic must be accepted and forwarded—regardless of whether it is TCP or UDP—the BIG-IP administrator must use a Standard virtual server, which is the only virtual server type designed for normal application traffic processing.

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In a large-scale BIG-IP environment with hundreds of virtual servers, the Network Map is the most effective tool for visualizing and auditing the relationships between various ADC objects.

The Network Map Functionality: The Network Map provides a hierarchical view of the local traffic objects. It allows an administrator to see the status and dependencies of Virtual Servers, Pools, Pool Members, and associated iRules all in one screen.

Search and Filter: By navigating to Local Traffic > Network Map, the administrator can use the Advanced Filter. This feature allows for searching specifically for an iRule name or a string within an iRule definition. Once the filter is applied, the system displays only the Virtual Servers that are associated with that specific iRule.

Efficiency: While the "Virtual Server List" (Option D) can be customized to show columns for iRules, it is often cumbersome to scroll through hundreds of entries. The "iRules List" (Option B) displays the scripts themselves but does not provide a reverse-lookup list of all associated virtual servers in a single view as efficiently as the Network Map.

Summary of Relationships: The Network Map is specifically designed to answer the question, "What is this object connected to?" making it the primary administrative interface for impact analysis during configuration changes.