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Edu_50128
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Aug 23, 2013

Communications problems between servers

Hi,

We have some problems with the comunications of some server. The situation is below:

  • Server A on VLAN 1 with IP 192.168.1.1/24
  • Server B on VLAN 1 with IP 192.168.1.3/24
  • Server C on VLAN 1 with IP 192.168.1.5/24
  • Virtual Server on VLAN 2 with IP 192.168.3.2/24 (its nodes are servers A and B)

The service is over http and https, and we are not using SNAT.

When clients from Internet try to connect to the Service there is no problem; but when server C ask for virtual server service, the connections never reach the server A or B. We just have this problem with connections over servers are in the same VLAN.

If we do a tcpdump we can see:

12:00:15.139092 IP 192.162.1.5.dyna-lm > 192.162.3.2.http: S 1702227370:1702227370(0) win 65535 <mss 1460,nop,nop,sackOK>

But the connection seems it doesn´t go out from the BIG-IP since in the servers A and B we cannot see any connection from server C or Virtual Server.

Any idea? Could you help me?

Thanks Regards

33 Replies

  • Done !!! And it works !! Thanks so much !!

     

    Its strange, and now the web page is loaded but it is loaded so slow... and from Internet there is no problem on it...

     

  • Its strange, and now the web page is loaded but it is loaded so slow

    you may run tcpdump on bigip to see what is going on.

     tcpdump -nni 0.0:nnn -s0 -w /var/tmp/output.pcap host x.x.x.x or host y.y.y.y or host z.z.z.z and port 80
    
    x.x.x.x is client ip
    y.y.y.y and z.z.z.z are pool member/server ip
    
  • With your tcpdump it doesn´t capture nothing...

     

    With this one, it works:

     

    tcpdump -i 0.0 -nn host 192.168.1.5 or host 192.168.1.3 or host 192.168.1.1

     

  • It was a free space problem on the BIG-IP, sorry. I´m going to analize the capture

     

    Thanks

     

  • Just analyze the capture we don´t see any issue with the traffic; we don´t see the responde from server 192.168.1.1 to server 192.168.1.5 because of the problems with the asymetric traffic you commented before.

     

    But, could it impact on the loaded webpages? Why is so slow the loading from comunications between servers and not from clients on Internet?

     

    Any idea or suggestion?

     

    Thanks

     

  • we don´t see the responde from server 192.168.1.1 to server 192.168.1.5

     

    i understand packet flow should look like this:

     

    1) 192.168.1.5 -> 192.168.3.2

     

    2) floating selfip on server vlan -> 192.168.1.1/192.168.1.3

     

    3) 192.168.1.1/192.168.1.3 -> floating selfip on server vlan

     

    4) 192.168.3.2 -> 192.168.1.5

     

    (1) and (4) are client-side (between client and bigip)

     

    (2) and (3) are server-side (between bigip and server)

     

  • Yes, it is this way.

     

    We have setting up the irule and the traffic goes this way.

     

    The problem we have now is the webpage is so slow loading... really really slow.

     

    Could be any configuration in the VS which affect to this behavior?

     

  • The problem we have now is the webpage is so slow loading... really really slow.

     

    in wireshark, you can show delta time between packet. can you check what causes the slowness?

     

  • if it is slow then probably it is waiting for something, perhaps a link to another system which doesn't work correctly because of this setup. use a browser tool like fire bug or build in with chrome (right click, inspect element) or such to determine what causes the hold up.