F5 GTM monitor generic host

Monitors can get complicated, as the behaviour changes per module, and even within the same module.

 

I had to test this in my lab to confirm.

 

Your understanding, and what I was expecting, is correct.

 

The GTM, maybe even another BIG-IP in the same data center, will monitor the generic host in that data center and report via iquery to the other GTM.

 

"What happen if site B monitor virtual server in generic host "Online" but site B monitor "Offline" ?"

 

I had to test, because there is a setting for that but talks about iquery.

 

The behaviour here was not what I was expecting.

 

I assume you mean virtual server up, and server (generic host) down.

 

Because site (I assume that being a data center) does not have monitor.

 

Interestingly, if you have gateway_icmp in the server, and http in the virtual server.

 

GTM will only perform http monitor.

 

If you remove the http monitor from the virtual server, GTM will monitor using gateway_icmp.

 

As GTM only uses the virtual server monitor, if both server and virtual server have monitor, the situation you describe will never happen.

 

However, if only have monitor in the server and that monitor is failing, both server and virtual server will be down.

 

I tried to play with virtual server status in the general settings, as per manual, it only affects iquery connections, so no impact to generic hosts.

 

https://support.f5.com/csp/article/K14938

 

All tests done in 14.0.0.