Re: [load balancing] F5 LTM marking nodes down

From: Seth Kusiak <SKusiak [izzat]>
Date: Thu Nov 08 2007 - 10:49:04 EST

If the traffic is not coming back then is means that the it's being lost
along the way. The problem may correct itself by the time you connect
telnet to the node from the stand by LTM.




From: [] On Behalf
Of Julian Grunnell
Sent: Thursday, November 08, 2007 4:39 AM
To: 'Load Balancing Mailing List'
Subject: Re: [load balancing] F5 LTM marking nodes down


Thanks Seth - ran a tcpdump on the internal vlan and captured all
traffic, what I can see is filtering for the nodes that get marked down
and icmp traffic only I can see that when the LTM logs nodes DOWN & UP
that the icmp traffic is not coming back from the nodes in question. BUT
as mentioned if I open up a new shell to the STANDBY LTM and ping the
node and also do "telnet <node-ip> 80" I get both the ping reply and a
port 80 connection.


Thanks - Julian.



        From: [] On
Behalf Of Seth Kusiak
        Sent: 07 November 2007 15:36
        To: Load Balancing Mailing List
        Subject: Re: [load balancing] F5 LTM marking nodes down

        I would run a tcpdump session from the standby LTM and capture
the monitor activity then analyze it. You'll be able to see if the LTM
has is incorrectly marking nodes as down or if there's an issue with
packets getting lost.




        From: [] On
Behalf Of Julian Grunnell
        Sent: Wednesday, November 07, 2007 10:14 AM
        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
        This e-mail is subject to:


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