F5CAB3 Exam Dumps : BIG-IP Administration Data Plane Configuration (F5CAB3) exam

The virtual server is configured for destination 192.168.21.50 , service port 53 , but its Protocol is TCP . Standard DNS query traffic is normally sent using UDP port 53 . Because virtual-server traffic matching includes the configured IP protocol, UDP DNS packets will not match a virtual server configured exclusively for TCP, causing the queries to fail.

F5 ' s DNS configuration guidance explicitly instructs administrators creating a DNS query virtual server to configure service port 53 and select UDP as the protocol. F5 also recommends separate TCP and UDP virtual servers when both forms of DNS traffic must be supported; TCP port 53 is particularly relevant for operations such as DNS zone transfers.

Option C is not required. The existing source network 192.168.100.0/23 spans addresses from 192.168.100.0 through 192.168.101.255, so both 192.168.101.100 and 192.168.101.200 are already permitted by the source-address criterion. F5 documents that the Source Address setting can specify the network from which a virtual server accepts traffic.

Therefore, changing the virtual server ' s Protocol from TCP to UDP corrects the traffic-matching problem.

Reference Topics: Virtual Server traffic matching; Protocol selection; DNS over UDP/TCP; Source Address matching; Service Port 53.

F5 provides several pre-configured (built-in) TCP profiles designed to optimize traffic for different network conditions. When an administrator is looking to improve general performance but does not have a specific, narrow use case (like strictly mobile or strictly long-haul WAN), the f5-tcp-progressive profile is the recommended starting point.

The f5-tcp-progressive profile is designed as a modern, high-performance replacement for the older default TCP settings. It incorporates several advanced congestion control algorithms and buffer management techniques that allow it to adapt dynamically to varying network latencies and packet loss scenarios. Unlike f5-tcp-legacy (Option A), which uses older, less efficient stacks, the progressive profile leverages modern TMM (Traffic Management Microkernel) optimizations.

While f5-tcp-mobile (Option B) is highly effective for high-loss cellular networks and f5-tcp-wan (Option D) is optimized for high-latency long-distance links, they can sometimes be too aggressive or poorly suited for standard campus or data center environments. The f5-tcp-progressive profile acts as a " best-of-all-worlds " template that typically provides an immediate performance boost for most web applications by improving window scaling and fast-retransmit behavior. Therefore, it is the procedural " first step " in TCP performance tuning before moving to more specialized, niche profiles.

Slow Ramp Time prevents new pool members from receiving a full share of traffic immediately, allowing applications to warm up gradually.