F5 F5CAB3 Dumps

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.

Least Connections (node) balances connections across the physical server regardless of how many services or pool members exist on that node.

A red diamond indicates that the Virtual Server is enabled but unavailable, typically due to all pool members being down.

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

BIG-IP provides several built-in TCP profiles optimized for different traffic patterns and network conditions. When attempting to improve general TCP performance, the recommended starting point isf5-tcp-progressive.

According to theBIG-IP Administration: Data Plane Configurationdocumentation:

f5-tcp-progressiveis designed as abalanced, general-purpose TCP optimization profile.

It dynamically adjusts TCP behavior to improve throughput and latency for most enterprise applications.

It is the recommended first-choice profile when tuning TCP performance before moving to more specialized profiles.

Why the other options are incorrect:

A. f5-tcp-legacyThis profile exists for backward compatibility and does not include modern TCP optimizations.

C. f5-tcp-mobileThis profile is optimized specifically for high-latency, lossy mobile networks and is not suitable for general-purpose environments.

D. No optionBIG-IP explicitly provides built-in TCP profiles for performance tuning; using none would forgo optimization opportunities.

Correct Resolution:

The administrator should first applyf5-tcp-progressiveto evaluate potential TCP performance improvements before considering more specialized profiles.

Performance (Layer 4) virtual servers rely on FastL4 profiles for high-speed Layer 4 traffic handling.

SSH is a TCP Layer 4 protocol. Applying an HTTP profile causes BIG-IP to expect HTTP headers, breaking SSH sessions. Removing the HTTP profile allows raw TCP forwarding.

SSH is aLayer 4 TCP-based protocolthat operates onTCP port 22and doesnot use HTTPin any capacity. In the exhibit, the Virtual Server is configured with anHTTP Profile applied, which is inappropriate for SSH traffic and causes connection failures.

According to theBIG-IP Administration: Data Plane Configurationdocumentation:

AnHTTP profile must only be applied to Virtual Servers handling HTTP or HTTPS traffic.

When an HTTP profile is attached, BIG-IP expects HTTP headers and attempts to parse application-layer data.

Non-HTTP protocols such asSSH, FTP (control), SMTP, and other raw TCP serviceswill fail if an HTTP profile is enabled.

Why the other options are incorrect:

A. Set Protocol to UDPSSH usesTCP, not UDP. Changing the protocol would break SSH entirely.

B. Set Source Address to 10.1.1.2The source address setting controls client access restrictions and is unrelated to protocol parsing issues.

C. Set Destination Address/Mask to 0.0.0.0/0The destination address is already valid for a specific SSH service and does not impact protocol handling.

Correct Resolution:

The BIG-IP Administrator shouldremove the HTTP Profile (set it to None)so the Virtual Server functions as a pure Layer 4 TCP service, allowing SSH connections to pass through successfully.

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

When multiple users share one source IP, source-address persistence fails. Cookie persistence uniquely identifies users at Layer 7 and ensures correct session handling.

X-Forwarded-For inserts the original client IP into HTTP headers while SNAT is enabled.

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