Bug ID 921477: Health monitors may fail when the HTTP RFC Compliance option is enabled in a dual BIG-IP setup.

Last Modified: Jan 20, 2023

Bug Tracker

Affected Product:  See more info
BIG-IP LTM(all modules)

Known Affected Versions:
13.1.0,,,,,,,,, 13.1.1,,,,, 13.1.3,,,,,,, 13.1.4,, 13.1.5,, 14.0.0,,,,,, 14.0.1,, 14.1.0,,,,,, 14.1.2,,,,,,,,, 14.1.3,, 14.1.4,,,,,,, 14.1.5,,,, 15.0.0, 15.0.1,,,,, 15.1.0,,,,,, 15.1.1, 15.1.2,, 15.1.3,, 15.1.4,, 15.1.5,, 15.1.6,, 15.1.7, 15.1.8,, 16.0.0,, 16.0.1,,, 16.1.0, 16.1.1, 16.1.2,,, 16.1.3,,,

Opened: Jun 26, 2020
Severity: 4-Minor


With the HTTP RFC enforcement profile option enabled, incoming health monitor requests without an HTTP version in the request line (HTTP/0.9) may fail to produce the correct result for dual BIG-IP configurations. This can result in incoming health monitor traffic being incorrectly blocked when traveling through a virtual server. These health monitors will be unable to provide the correct availability of the intended resource. The default HTTP and HTTPS monitors as well as any custom monitors with a missing HTTP version in their requests could see this issue.


Rather than receiving the correct health check result, the original BIG-IP system can fail to report whether the second BIG-IP is available.


A dual BIG-IP configuration may provisioned with the following considerations. -- One or more BIG-IP systems are in the network path for monitor traffic. -- The first BIG-IP system uses a health monitor that initiates a health check request (without an HTTP version) in the request line (HTTP/0.9) against a second BIG-IP system. -- The second (downstream) BIG-IP system has a virtual server that is the endpoint for the monitor. The virtual server is configured with an HTTP profile with the HTTP RFC Compliance profile option selected.


You can use http_head_f5 monitor to perform health checks.

Fix Information


Behavior Change