Users are unable to reach an application. The BIG-IP Administrator checks the Configuration Utility and observes that the Virtual Server has a red…

A red diamond icon next to a virtual server indicates its status is "Unavailable." This means the virtual server is enabled but cannot process traffic because its required resources are not available. This status typically occurs when the associated pool(s) are also marked as unavailable. A pool becomes unavailable if all of its members are marked "down" (e.g., by a failed health monitor) or have been administratively "disabled." Therefore, both all pool members being down and all pool members being disabled are valid causes for this issue.

B. Receiving incorrect traffic might cause connection resets but does not directly change the virtual server's availability status icon to red.

C. A disabled virtual server is marked with a black diamond (or black circle), indicating it has been administratively taken offline.

1. F5 Networks. (2021). BIG-IP Local Traffic Manager: Concepts. Chapter 3: Virtual Servers. The section on "Virtual Server Status" describes the various status icons.

2. F5 Knowledge Center. (2022). K13310: BIG-IP object status icons. This article explicitly defines the red diamond as "Unavailable - The object is not available for load balancing." It clarifies this state for a virtual server is often due to all associated pool members being unavailable.

3. F5 Networks. (2021). TMOS Management Guide for BIG-IP Systems. Chapter 15: Monitoring the Health of the System. This guide explains how health monitors mark pool members down, which in turn affects pool and virtual server status.