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Muhammad_Irfan1's avatar
Muhammad_Irfan1
Icon for Cirrus rankCirrus
Feb 28, 2015

Pool members goes down where as application is running

We are facing a problem.   There are about 40 pools defined in LTM and each have 2 or 3 members. All of them are monitored on TCP-halfopen monitor which monitors pool members on the bases of TCP...
StephanManthey's avatar
StephanManthey
Icon for Nacreous rankNacreous
Feb 28, 2015

Hi Muhammad,

this pool is monitored as well via tcp_half_open only, if I understood your question right.

You can see the pool member toggling as well in /var/log/ltm?

I would recommend to run a trace while observing the issue: 
tcpdump -nnni 0.0 -s 0 -e 'host  and (host  or host )'

Just replace "bigip_self_ip" with the serverside self IP of the BIG-IP you are running the trace on (as it is used for healthchecking) and the "node_0(1|2)" by the pool member IPs.

The tcp_half_open should show a SYN sent by BIG-IP, SYN-ACK response from node, followed by RESET from the BIG-IP.

Perhaps your server folks are running an IDS/IPS?

Did you already try to use an increased monitoring interval?

I would be interested in your findings. What TMOS version are you on?

Thanks, Stephan