11.5.1-HF3 - LTM monitor Resets

Hi,

 

I have a little problem with my new systems, which are running with 11.5.1-HF3.

 

At the moment, there is no active traffic on the systems. Only monitoring of the backend from my configured pools.

 

Here I can see, that a random pool sometimes is going down for a small time.

 

With wireshark I can see, that the bigip sometimes reset the connection of the haelthcheck and sends an ICMP unreachable to the backend. After 9 seconds everything is ok again.

 

The timeout of the member is 5 seconds, the monitor is default tcp.

 

With a http monitor - timout 10 seconds -, I allways have a downtime of 15 seconds.

 

It allways looks the same:

 

BIGIP sends a SYN

 

Backend sends a SYN, ACK

 

BIGIP sends a Destination unreacheable

 

BIGIP sends a RST, ACK

 

There is everywhere a cnnection limit of 0.

 

Anyone have an idea?