Frequent Health monitors bouncing - Help

Hi all,

 

 

I need assistance on a strange issue on my bigip and I need help to understand what could be.

 

 

We have 2 bigip machines in sync (one active and one standby) that are obviously identically configured and the issue is about a frequent down/up of the nodes of a particular pool due to their monitor bouncing. Sometimes a node goes down, sometimes the other one and sometimes both. After a minute they back online.

 

 

The strange thing is that the nodes have no issues that can cause the down of their monitor and mainly that while the active bigip has these constant monitor down/up on those nodes monitor, the standby one had never reported a single monitor failure on them. This bouncing affects only active bigip while the standby has no issue and has never seen them down.

 

 

I can add also that nodes have no connectivity issue with the active bigip because everytime the monitor goes down their status (icmp) is always green.

 

 

The monitor is basically just a get of a web page, but I tried adding also a generic TCP get as a second monitor configuring pool to have just 1 of them up to be ok but without success. In this case sometimes a monitor goes down, sometimes the other one and frequently both ... and the node goes red.

 

 

What could cause this issue? Maybe a high number of concurrent connections explaying why the standby bigip had never seen those monitor down, even if I have no connection limit in VIP and nodes config? A sort of autodefence of bigip that put a monitor down when "something" happens? The servers that for some issue warms bigip to stop to use them and then it shutdown the monitor? Bug?

 

 

In other words, in wich states a health monitor of a node goes down even if the monitored service is correctly up and running?

 

 

 

Any help is appreciated

 

 

Thank you