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Dropped connection to server

Discussion in 'Networking' started by JasonZA, Jul 9, 2018.

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  1. JasonZA

    JasonZA Thread Starter

    Joined:
    Jul 9, 2018
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    Hi All

    Have a bit of a strange problem here.

    In a nutshell, I have an issue where client connects to a server but then unexpectedly drops.
    I have clients from a 172.x.x.x range which connect and get no disconnects but then have clients in a 192.x.x.x range which can connect but then get unexpected disconnects.

    I have a packet capture and if I understand correctly the client in the 192.x.x.x range is sending TCP ACKs but the server is not receiving them so this results in the client sending duplicate ACKs and eventually the server does a TCP Retransmitt.

    both subnets connect over the same infrastructure and have the same configuration on the switching and routing devices.
    Firewall and ATP have pretty much been disabled in order to troubleshoot this so we have confirmed its not that.

    We run a ping to the server and they are continuous with no drops but the clients still disconnect
    Some servers in the range are worse than others, i.e more disconnects, etc
    With the ping being consistent, no drops, this seems to eliminate anything physical.
    Each retransmitt shows a packet size of 1514, thinking it might be MTU but not sure, which would explain why the pings go through but still get disconnects, waiting for the client to retest with a ping size of 1514

    I am thinking that the server in question that is the issue but not sure how to proceed and / or what to look at...

    Hoping someone can point me in the right direction
     
  2. TerryNet

    TerryNet Moderator

    Joined:
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    Messages:
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    First Name:
    Terry
    Please explain your network, especially the why/how you have the two IP subnets.

    The server has a 172... IP address?
     
  3. JasonZA

    JasonZA Thread Starter

    Joined:
    Jul 9, 2018
    Messages:
    2

    Its just the way the client has their network configured, two different zones on an SRX, so for security reasons
    but both zones are configured identically

    The server has a public IP address which I cannot disclose
     
  4. TerryNet

    TerryNet Moderator

    Joined:
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    Messages:
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    First Name:
    Terry
    Beyond me; I cannot be of help.
     
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