Forum Discussion
AltostratusDefault Health Monitor - GSLB
EmployeeThe bigip server monitor for LTMs reports the status of the LTM virtual server to the GTM via iQuery.
When the LTM pool members go down due to failing monitors, the status of the virtual server changes on the LTM, and the GTM is alerted via iQuery.
Other GTM monitors probing the GTM pools are in addition to the server object level bigip monitor.
- jkramer9
Thanks, this is what I originally suspected.
I tried searching around and couldn't find an answer which explains how the bigip server monitor functions. Does the GTM simply do a ping request to the LTM Virtual Servers every 30 seconds to check availability status and is the hold down timer 90 seconds before it's marked as Down?
- Simon_Blakely
> Does the GTM simply do a ping request to the LTM Virtual Servers every
> 30 seconds to check availability status
It's way more complex than that - the GTM schedules probe requests to big3d processes on LTMs in the Datacenter, which is then responsible for probing othet LTMs via iQuery. The status of virtual servers is determined directly from the LTM internal state tracking (based on the LTM pool monitors).
> and is the hold down timer 90 seconds before it's marked as Down?
This is controlled by the "ignore-down-response", which is disabled by default.
This will mark down LTM virtual servers immediately (because the defined pool monitor has already expired to mark the virtual server down).
If "ignore-down-response" is enabled, then the timeout period has to expire before the GTM marks the server object down.
- jkramer9
Got it, thanks for the clear explanation.
One last thing I'm curious about. If an LTM Virtual Server goes down (on a standard http health monitor check, that would be 3 failed health checks, meaning at the 16s mark), at what point is that corresponding Pool Member on the GTM marked down? Would it be immediate at the 16s mark where the LTM notifies the GTM of it's Down status?
Thanks
