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Julian_Kippels_'s avatar
Julian_Kippels_
Icon for Nimbostratus rankNimbostratus
Jul 04, 2016

Connections with virtual server lost?

Hi,

 

I am experiencing strange bugs with my mail servers. The servers are behind a virtual server IP. Usually every connection to those servers is logged by them. But sometimes I am notified by other admins, that their servers could not send mails to mine. Their logs state, that the connection to my server is lost. I cannot see any connection attempts on my end. I assume that sometimes the load balancer isn't handing the connection over to the backend servers correctly, or else I would see the connection logged.

 

Any suggestion on how I could confirm my suspicion, or better yet, has anyone experienced similar problems and has a solution?

 

Thanks in advance, Julian

 

application delivery
BIG-IP
LTM

3 Replies

  • tatmotiv's avatar
    tatmotiv
    Icon for Cirrostratus rankCirrostratus
    Jul 04, 2016

    You could start checking the statistics of your tcp profile (virtual server -> statistics -> select tcp profile at the bottom). Maybe there you can find some counters pointing you into the right direction. Also, the /var/log/ltm logfile might contain useful information. If that doesn't give you any insight, try capturing those faulty connection attempts with tcpdump. If you cannot see the erroneous connection attempts there at all, some device before the BigIP might be causing problems (router, firewall...).

     

    HTH

     

    Martin