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

This scenario combinessession continuity,multiple protocols (HTTP and FTP), andHA failover behavior, which directly implicatespersistence handling across devices and services.

Key Requirements Breakdown

Samepool member for entire session

Session must survivefailover

Session must spanmultiple services (HTTP and FTP)

Why Persistence Mirroring + Match Across Services Is Required

Persistence Mirroring

Ensurespersistence records are synchronizedfrom the active BIG-IP to the standby BIG-IP.

Without mirroring:

After failover, the standby device hasno persistence table

Clients are load-balanced again

Sessions break, forcing users to restart

Persistence mirroring is essential forsession continuity during failover

Match Across Services

Allows asingle persistence recordto be shared acrossmultiple virtual servers / protocols

Required when:

HTTP and FTP must use thesame pool member

Multiple services are part of a single application session

Together, these settings ensure:

Persistence survivesdevice failover

Persistence is honoredacross HTTP and FTP

Why the Other Options Are Incorrect

A. Cookie persistence and session timeoutCookie persistence only applies to HTTP and does not address FTP or failover synchronization.

B. Stateful failover and Network Failover detectionStateful failover applies toconnection state, notpersistence records, and does not link HTTP and FTP sessions.

D. SYN-cookie insertion threshold and connection low-water markThese are DoS / SYN flood protection settings, unrelated to persistence or HA behavior.

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.

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

In BIG-IP, atrunkis a Layer 2 network object used to aggregate multiple physicalinterfacesinto a single logical link. This aggregation providesincreased bandwidthandlink resiliency, commonly in conjunction with LACP.

Key concepts that apply here:

Trunks are managed under the/net trunktmsh hierarchy

Physical interfaces are added or removed using themodifycommand

Thecreatecommand is used only when defining a brand-new trunk, not when updating an existing one

Because the trunk already exists and the goal is toadd interfaces, the correct operation is:

tmsh modify /net trunk trunk_A interfaces add {1.3 1.4}

This command:

Modifies the existing trunk named trunk_A

Adds interfaces 1.3 and 1.4 to the trunk

Immediately increases available bandwidth and redundancy

Why the Other Options Are Incorrect

Buses the /sys hierarchy, which is not used for trunks

Cattempts to create a trunk that already exists

Duses an incorrect hierarchy and an incorrect operation

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

The diagram illustrates a specific TCP handshake sequence where the BIG-IP system acts as a transparent forwarder rather than a full proxy. The key indicators that identify this as aForwarding (IP) virtual serverare as follows:

Initial Packet Processing: The diagram explicitly states that the LTM evaluates the packet lookingonly at the destination IP address. This is the fundamental characteristic of a Forwarding IP virtual server, which uses the system's routing table to make forwarding decisions instead of load balancing to a pool of members.

Handshake Sequence: Unlike aStandardvirtual server, which completes the three-way handshake with the client (SYN, SYN-ACK, ACK)beforeinitiating a separate connection to the server, the Forwarding IP virtual server passes the client's originalSYNpacket directly to the destination node.

Response Timing: The BIG-IP system waits for theSYN-ACKfrom the destination node before it sends a SYN-ACK back to the client. It essentially "passes through" the handshake signals while still maintaining a state entry in the connection table to track the flow.

Packet-by-Packet Logic: While it tracks the state, it does not perform address translation (unless SNAT is specifically configured) or deep packet inspection like a full proxy would.

Why other options are incorrect:

Standard virtual server: A Standard virtual server is a "full proxy." It would finish the handshake with the client first and only then open a second, independent TCP connection to the backend server.

Stateless virtual server: A stateless virtual server does not track connections in the connection table. The diagram shows the system meticulously passing sequence numbers ($seq\_num$) and acknowledgment numbers ($ack\_num$) between the two sides, which requires stateful tracking of the TCP flow.

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

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 andforwards traffic to pool members

Supports bothTCP and UDPtraffic

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

Required when the goal is toprocess 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 beforwarded

Only aStandard virtual serverforwards 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 beaccepted and forwarded—regardless of whether it is TCP or UDP—the BIG-IP administrator must use aStandard virtual server, which is the only virtual server type designed for normal application traffic processing.

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