サンプル問題 1： 168.2.150 All DNS queries destined for the external DNS servers fail. Which property change should the BIG-IP Administrator make in the Virtual Server to resolve this issue? (Choose one answer)
A: Protocol profile (Client) to DNS_OPTIMIZED
B: Type to Performance (HTTP)
C: Source Address to 192.168.10.0/24
D: Protocol to UDP
正解：D
Explanation: DNS traffic is primarily transported using UDP port 53. In the exhibit, the Virtual Server is configured with the Protocol set to TCP, which prevents standard DNS queries from being processed correctly. BIG-IP Virtual Servers must be configured with the correct Layer 4 protocol to match the application traffic they are handling. According to the BIG-IP Administration: Data Plane Configuration documentation: The Protocol setting on a Virtual Server defines whether traffic is processed as TCP, UDP, or another supported transport protocol. Standard DNS queries and responses use UDP, while TCP is only required for DNS zone transfers (AXFR) or exceptionally large responses. When a DNS Virtual Server is incorrectly configured with TCP, UDP-based DNS queries are dropped, causing all requests to fail. Why the other options are incorrect: A. Protocol profile (Client) to DNS_OPTIMIZED A DNS profile enhances DNS functionality but does not correct an incorrect transport protocol configuration. B. Type to Performance (HTTP) Performance (HTTP) Virtual Servers are designed for HTTP traffic and are not suitable for DNS services. C. Source Address to 192.168.10.0/24 The existing source IPs already fall within the allowed range, so this setting does not address the failure. Correct Resolution: Changing the Protocol to UDP aligns the Virtual Server with standard DNS transport requirements, allowing DNS queries to be successfully processed and load-balanced.
サンプル問題 2： A BIG-IP Administrator finds the following log entry after a report of user issues connecting to a virtual server: 01010201: Intercept exhaustion on 10.70.110.112 to 192.28.123.250:80 (proto 6) How should the BIG-IP Administrator modify the SNAT pool that is associated with the virtual server? (Choose one answer)
A: Increase the timeout of the SNAT addresses
B: Remove the SNAT pool and apply SNAT Automap
C: Remove an IP address from the SNAT pool
D: Add an IP address to the SNAT pool
正解：D
Explanation: 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 the BIG-IP Administration: Data Plane Configuration documentation: 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 an Intercept exhaustion error and new connections fail. The recommended resolution is to increase the available SNAT resources by adding additional IP addresses to the SNAT pool. Why the other options are incorrect: A. Increase the timeout of the SNAT addresses Increasing timeouts may actually worsen the problem by keeping ports allocated longer, accelerating port exhaustion. B. Remove the SNAT pool and apply SNAT Automap SNAT 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 pool This would reduce the number of available source ports and further exacerbate the intercept exhaustion condition. Correct Resolution: By adding 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.
サンプル問題 3： A BIG-IP Administrator uses backend servers to host multiple services per server. There are multiple virtual servers and pools defined, referencing the same backend servers. Which load balancing algorithm is most appropriate to have an equal number of connections on each backend server? (Choose one answer)
A: Least Connections (node)
B: Predictive (member)
C: Least Connections (member)
D: Predictive (node)
正解：A
Explanation: In this scenario, each backend node (server) hosts multiple services and is referenced by multiple pools and virtual servers. The goal is to ensure an equal number of total connections per backend server, regardless of how many pool members (services/ports) exist on that server. According to the BIG-IP Administration: Data Plane Configuration documentation: Least Connections (node) tracks the total number of active connections to a node across all pool members and services. This algorithm ensures load distribution is balanced at the server level, not just at the individual service (member) level. It is specifically recommended when: Multiple pool members exist on the same backend server Multiple virtual servers reference the same backend servers Why the other options are incorrect: B. Predictive (member) Predictive algorithms are advanced and traffic-pattern based, but they operate at the member level and do not guarantee equal connections per server. C. Least Connections (member) This balances connections per pool member, which can overload a server hosting multiple members while still appearing “balanced” per member. D. Predictive (node) Although node-aware, predictive algorithms are less deterministic and not the best choice when strict equality of connections is required. Correct Resolution: Using Least Connections (node) ensures that each backend server carries an equal connection load across all services and pools.
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