Bug ID 743444: Changing monitor config with SASP monitor causes Virtual to flap

Last Modified: Jan 20, 2023

Bug Tracker

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

Known Affected Versions:
12.1.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1, 12.1.1 HF1, 12.1.1 HF2, 12.1.2, 12.1.2 HF1, 12.1.2 HF2, 12.1.3,,,,,,,, 12.1.4,, 12.1.5,,,, 12.1.6, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.0.1, 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,,,,

Opened: Sep 10, 2018
Severity: 3-Major


If you change the monitor configuration for a pool or pool member to include the SASP monitor and add or remove an additional monitor (e.g., TCP), the pool members affected by this configuration change will be marked Down/Unavailable (RED) for some period of time (e.g., 5 seconds) after the change. During this time, if all pool members are marked down, any virtual servers associated with the pool are also marked down, interrupting traffic.


Pool members affected by the monitor change are marked down by the SASP monitor until the SASP monitor receives member weights from the SASP GWM. If the monitor configuration change affects all pool members in a pool, any virtual servers configured to use that pool are also marked down during this period.


This occurs when changing the configured monitor for a pool or pool member in one of the following ways: 1. From a SASP monitor to a SASP plus another monitor. 2. From a SASP monitor plus another monitor, to a SASP monitor. 3. From a SASP monitor plus another monitor, to a SASP monitor plus a different monitor.


If some members of the pool are configured to use a different monitor than the other pool members, only a subset of pool members are marked down as the result of the monitor configuration change, and the corresponding virtual servers are not marked down due to the monitor configuration change.

Fix Information


Behavior Change