I need your support urgently as I've a problem in the connection between 2 servers. Here's the below when the connection became down, but this is from the other side so I can't identify what is it ? Ping, Telnet or Trace... I know the operation of all of them but I'm confused what is this about.

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Thanks in advance and will wait your reply.

  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Aug 16, 2017 at 22:06

1 Answer 1


All the packets in your capture are SYN packets. It is the first step of the process of establishing a TCP connection.

It seems one one device try to establish a connection with a server, and the server doesn't respond, and the device keep trying.

Why the server doesn't respond, we cannot say, it can be a firewall rule or the service on the server that doesn't work properly.

You could check the there's actually something listening on the TCP port involved with the netstat command and check your application log.

  • Thanks for your reply, really appreciated , Actually the setup is < Linux Server -- GW ----- FW -- Server > The linux server is trying to connect to the Server , When this connection is down , I can ping normally from FW to GW and the IPSec between them is up, so I consider from this point that the connection between GW and FW is stable, so as you mentioned may be the problem in the service itself ? What is your recommended TSHoot for this issue ?? Feb 17, 2017 at 8:22
  • I would perform a capture on the server itself to see A ) if incoming packet are coming through, B) if the server send a response. If A is OK and B is KO then investigate on the server. If both are OK, look on all intermediate network device to check where packets are dropped
    – JFL
    Feb 17, 2017 at 8:41
  • Thanks a lot :) adding to that also, there are many linux servers are communicating with this server [ those linux servers are in different networks ] ... also when the connection is down , the VPN is up but no sessions are received from the linux server so I [ as a FW ] can reach GW only as VPN is up and can ping it as well. so A & B options are not applicable in this update..... Feb 17, 2017 at 12:19

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