F5 Networks F5CAB3 Exam Dumps

The exhibit shows the advanced configuration of a VLAN where the Fail-safe option is checked. VLAN Fail-safe is a high-availability feature used to monitor network connectivity on a specific VLAN. When enabled, the BIG-IP system monitors the VLAN for network traffic. If the system does not detect any 'useful' traffic on the VLAN within the specified Fail-safe Timeout (which is 90 seconds in the exhibit), it attempts to generate traffic by pinging the default gateway or other devices. If it still detects no traffic, the BIG-IP concludes that the VLAN is unreachable or the network interface has failed, and it triggers a 'Fail-safe Action'---in this case, 'Reboot' or a failover to the peer device in the HA group.

Because the administrator has just created a new VLAN that 'does NOT yet have any traffic,' the Fail-safe mechanism triggers immediately after the 90-second timeout period. Since no devices are yet communicating on this VLAN, the BIG-IP incorrectly assumes there is a hardware or cabling failure and forces a failover to ensure the standby device (which might have better connectivity) takes over. To prevent this unwanted failover, the administrator should uncheck the Fail-safe box for that specific VLAN until the VLAN is fully populated with active nodes and regular traffic. Once the application is live and traffic is flowing, Fail-safe can be re-enabled to provide an additional layer of redundancy. Auto Last Hop (Option A) and Source Check (Option B) are routing and security features that do not trigger HA failover events.

Similar to the logic required for managing multi-service backend environments, the issue described---where servers hosting multiple protocols like FTP and HTTP are experiencing uneven distribution---stems from the BIG-IP's default behavior of treating each pool independently. If the administrator uses a member-based load balancing method, the BIG-IP distributes HTTP traffic regardless of how much FTP traffic that same physical server is currently processing.

To resolve this, the administrator must utilize the Least Connections (Node) method. By switching both the HTTP and FTP pools to this algorithm, the BIG-IP begins to make load balancing decisions based on the total combined connection count for the IP address of each server. When a new HTTP request arrives, the BIG-IP checks which server has the fewest total connections (including existing FTP sessions). This prevents a server that is already busy with long-lived FTP transfers from being overwhelmed by a sudden burst of HTTP requests.

Ratio methods (Options A and C) are static and rely on the administrator manually assigning weights to servers based on their perceived capacity; they do not adapt to real-time fluctuations in traffic volume across different pools. Least Connections (Member) (Option B) remains blind to the 'cross-pool' traffic on the same hardware. Only the Node-based Least Connections approach provides the global visibility necessary to 'even out' the total resource utilization across servers supporting multiple distinct applications.

To fulfill the requirement of 'SSL Offload' limited to 'TLSv1.2 only,' the administrator must focus on the client-side of the connection. SSL Offload means the BIG-IP terminates the encrypted connection from the user, processes the traffic (often as plain text internally), and optionally sends it to the backend. The profile responsible for this termination and the initial negotiation with the client's browser is the Client SSL Profile.

A custom Client SSL Profile must be created because the default clientssl profile typically allows a broad range of protocols for compatibility (including TLS 1.0, 1.1, and 1.2). To restrict communication specifically to TLS 1.2, the administrator modifies the Ciphers string within the profile. Using a string such as DEFAULT:!SSLv3:!TLSv1:!TLSv1.1 or specifically defining TLSv1.2-only suites ensures that the BIG-IP will reject any handshake attempts from older, less secure protocols.

Server SSL Profiles (Options B and C) are used for the encryption between the BIG-IP and the backend nodes, which is not what is requested here. Simply selecting 'no TLSv1' in an options list (Option D) is insufficient and often refers to older versions of the software; the modern and standard way to control protocol negotiation on a BIG-IP is through the precise application of Cipher Strings within the Client SSL profile. This ensures compliance with security standards like PCI-DSS while providing the offloading benefits to the backend infrastructure.

Connection rate limits restrict how many new connections are accepted per second, protecting application resources.

WAN-optimized TCP profiles improve performance for high-latency Internet clients, while LAN profiles are optimal for backend servers.