Re: [load balancing] F5 LTM marking nodes down

From: Julian Grunnell <julian.grunnell [izzat]>
Date: Thu Nov 08 2007 - 04:40:30 EST

Thanks, don't think this is the issue though as the ACTIVE LTM NEVER marks
the nodes down, but the STANDBY does - the config is synced from the ACTIVE
TLTM. But yep, ALL the monitors have reasonable timeouts and NOT the
standard 5 & 16 secs as is the default.


From: [] On Behalf Of
LeMay, John
Sent: 07 November 2007 15:49
To: Load Balancing Mailing List
Subject: Re: [load balancing] F5 LTM marking nodes down

A possible resolution, really a workaround, may be to use custom monitors
for http and icmp with increased timer and interval values. I've done this
in the past for different reasons, and it doesn't tell you where the issue
is of course. If you do go this route, F5 has recommended to me in the past
that the timeout should always equal three times the interval plus one
second (the online help recommends the same). This may even give a clue to
the root cause of the issue. If you increase the timeout and interval and
the issue goes away, chances are the issue is latency of some sort.
If you can get this to happen at predictable times, you could always run
tcpdump on the standby box during that time period and see if there are any
clues in the trace.

John LeMay 
K. Hovnanian Companies, LLC 
Systems Engineer 
Ph. 732 383-2195 
From: [] On Behalf Of
Julian Grunnell
Sent: Wednesday, November 07, 2007 10:14
Subject: [load balancing] F5 LTM marking nodes down
Hi - got a query regarding alerts that a STANDBY LTM 1500 is generating, we
have a pair of LTM 1500's in an ACTIVE / STANDBY setup using vlangroups.
Version 9.3.0 is installed. The nodes behind the LTMs are Microsoft 2003 IIS
6.0 servers using ACTIVE / PASSIVE NIC teaming.
We see on a daily basis the STANDBY LTM marking nodes as DOWN and then UP
for both icmp and HTTP health checks, often a minute or two inbetween the
state changes, the ACTIVE LTM NEVER logs anything.
At the times the alerts are seen the guys that admin the web servers cannot
see anything wrong at all - the servers are up and running. And the guys
that admin the network infrastructure cannot see any errors at all from any
of the switchports. What I have seen is that when the STANDBY LTM has the
node marked DOWN I can both ping the node in question and make a port 80
connection from the STANDY LTM which is just bizarre.
If anyone has any ideas on where the problem might lie, things that would be
worth checking or even better have had this problem before and how to
resolve it I would appreciate it!!
Thanks - Julian.
Julian Grunnell
3rd Line Technical Support
Pipex Communications
Tel: 01296 300227
Mob: 07803 649593
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Received on Thu Nov 8 04:52:21 2007

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