Free Practice Questions for F5 F5CAB3 Exam

Persistence overrides load balancing decisions by maintaining client-to-server affinity.

WAN TCP profiles are optimized for high latency and packet loss typical of Internet clients, while LAN profiles are ideal for backend servers.

By default, BIG-IP load balancing algorithms (such as Round Robin) distribute connections evenly across all available pool members. However,persistence profiles override normal load balancing decisionsby forcing subsequent connections from a client to be sent to the same pool member.

According to theBIG-IP Administration: Data Plane Configurationdocumentation:

Persistence creates aclient-to-server mappingthat is honored before load balancing algorithms are applied.

When persistence is enabled, BIG-IP may repeatedly select the same pool member even if others are available.

This directly alters load balancing behavior.

Why the other options are incorrect:

A. Adding a OneConnect profileOneConnect optimizes server-side TCP connections but does not change which pool member is selected.

B. Enabling SNAT automapSNAT affects source address translation, not pool member selection.

C. Enabling a fallback host in the HTTP profileA fallback host is only used when no pool members are available.

Correct Resolution:

Adding apersistence profilealters load balancing behavior by maintaining client affinity to a specific pool member.

Forwarding (IP) virtual servers forward traffic based on routing decisions and do not use pools or pool members.

Application-specific health checks must validate application responses, which requires HTTP monitors with custom send/receive strings.

From the exhibit, the pool containsdifferent applications on different service ports(for example, HTTP/80, FTP/21, HTTPS/443, SSH/22). To mark pool members correctly, BIG-IP must be able to verify theactual servicerunning on each member’s port.

InBIG-IP Administration: Data Plane Configuration, monitor behavior is described as follows:

Whenmultiple monitorsare assigned to a pool, theAvailability Requirementcontrols how monitor results are evaluated:

At least one= the pool member is markedupifany oneof the assigned monitors succeeds.

All= the pool member is markeduponly ifeveryassigned monitor succeeds.

For pools containing members with different services/ports, usingAllcan incorrectly mark members down because monitors intended for other services will fail on the wrong port.

WhyCis correct:

AssigningHTTPS, HTTP, FTP, and SSHcovers the actual services shown in the pool.

Setting the Availability Requirement toat least oneensures that each pool member is consideredavailablewhen itsappropriateservice monitor succeeds, without being forced to pass unrelated service monitors.

Why the other options are incorrect:

A / D (Availability Requirement = all):would cause members to be markeddownwhen unrelated monitors fail (e.g., SSH monitor against an HTTP member).

B (includes ICMP):ICMP can indicate the host is reachable even if theapplication service is down, which does not “accurately” reflect service availability.

Therefore, the best choice isHTTPS, HTTP, FTP, and SSHwith Availability Requirement ofat least onehealth monitor.

The log message“Intercept exhaustion”indicates that the BIG-IP system has exhausted the available source port translations for one or more SNAT addresses. This occurs when too many concurrent client connections are being translated through a limited number of SNAT IP addresses, and all ephemeral source ports (typically ~64,000 per SNAT IP) are in use.

According to theBIG-IP Administration: Data Plane Configurationdocumentation:

Each SNAT IP address provides a finite number of available source ports.

When the number of concurrent connections exceeds the available port space, the BIG-IP logs anIntercept exhaustionerror and new connections fail.

The recommended resolution is toincrease the available SNAT resourcesby adding additional IP addresses to the SNAT pool.

Why the other options are incorrect:

A. Increase the timeout of the SNAT addressesIncreasing timeouts may actually worsen the problem by keeping ports allocated longer, accelerating port exhaustion.

B. Remove the SNAT pool and apply SNAT AutomapSNAT Automap uses the Self IP addresses on the egress VLAN, which may not provide additional capacity and can introduce routing or design issues. This is not a direct or recommended fix for SNAT exhaustion.

C. Remove an IP address from the SNAT poolThis would reduce the number of available source ports and further exacerbate the intercept exhaustion condition.

Correct Resolution:

Byadding an IP address to the SNAT pool, the BIG-IP increases the total number of available source ports, alleviating intercept exhaustion and restoring successful client connections.

This scenario requiresunequal load distributionbased onserver capacity. The newer servers must receive more connections than the older ones, while still dynamically accounting for active connection counts.

According toBIG-IP Administration: Data Plane Configurationdocumentation:

Weighted Least Connections (member)combines:

Connection awareness(least connections)

Administrator-defined weights (ratios)to reflect server capacity

Pool members withhigher weights receive proportionally more new connectionsthan members with lower weights, even when using the same load balancing algorithm.

WhyBis correct:

Allows assigninghigher weights to newer serversand lower weights to older servers

Ensures smarter traffic distribution based on bothcapacity and real-time load

Why the other options are incorrect:

A. Global AvailabilityUsed for disaster recovery and site failover, not intra-pool load distribution.

C. Round RobinDistributes connections evenly without considering server capacity.

D. Least Connections (member)Balances only by current connection count and does not account for differences in server performance or capacity.

Correct Resolution:

UseWeighted Least Connections (member)and assignhigher weights to newer serversso they receive more traffic while protecting older servers from overload.

When many users share one source IP, source-address persistence fails. Cookie persistence uniquely identifies clients at Layer 7.