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Resolved VMware server and lots of SYN packets...

Discussion in 'Networking (Hardware & Software)' started by batsona, 2012/05/10.

  1. 2012/05/10
    batsona

    batsona Well-Known Member Thread Starter

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    At center-stage, we have an ESXi server with ~30 virtuals running on it. (Virtuals are WinXP SP3) Each Virtual has a client installed for a Patch Management solution from Dell, called "KACEâ€. Recently I took the KACE srvr off the network to back it up, and those 30 virtuals became sluggish. Everything went back to normal when I put the KACE server back on the network.

    On the network side, the virtuals started sending SYN packets to the KACE server, which end up as an "˜AGE-OUT’ on the firewall protecting the KACE server. This is being done about 175 times a minute. (I know, that’s only 3-4 per machine per min, which is not a lot)

    Our hypothesis: There’s something related to how the ESXi server deals with this SYN / AGE-OUT condition that causes resource problems, or other problems that slow down the virtuals. The volume of this traffic is insignificant, but perhaps ESXi is having problems processing it somehow.


    Any ideas?
     
    batsona,
    #1
  2. 2012/06/20
    TonyT

    TonyT SuperGeek Staff

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    You probably saw this already:
    http://communities.vmware.com/message/1141559

    Verify that the ESXi's ACKs are getting through to the virtuals. If the firewall appliance is blocking, holding or filtering the SYNs, then it's quite possible that the ACKs are also being held up, or the ACKs are ACKing SYNs that have since timed out.

    It could also have something to do with the ESXi's iptables config, whay may or may not be editable in your setup. I've only done a small amount of reading re ESXi, but from what I remember, it doesn't have the CLI interface.
     
    TonyT,
    #2


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  4. 2012/06/20
    batsona

    batsona Well-Known Member Thread Starter

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    I'll fwd this to our network team & see what we can find. ---The main idea here is:

    Virtuals sending SYNs & not receiving RST's = resource issues / RDP sluggishness

    Virtual sending SYNs and do receive RST's for those syns = no impact whatsoever.
     
    batsona,
    #3

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