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  • linux server doesnt respond to pings kinda...

    this is a new one to me...

    im not a linux guru by any means, so maybe im missing something basic.

    i have a linux server (RHEL 4) that runs a child support application. its a terminal emulation program... the users connect with a telnet connection to access an informix dB.

    this application works fine from my desktop. it works fine on client stations on the 1st floor, which is on VLANs 1,2 and 3. they are the 192.168.1-5.XXX addresses...

    the fourth floor is on a separate VLAN. the clients up there have special printers, and to segment these printers, there is a separate VLAN. its the '40' VLAN... so clients get an address like 192.168.40.200...

    when i try to connect to the application via a telnet, nothing happens. i can "C:> nslookup lincse" and get back the correct IP (192.168.5.170) when i try to ping lincse.mydomain.com i get "no response"...

    BUT
    if i go to the linux server ad ping the client station "root# ping 192.168.40.200" i get all responses back and magically the client can now ping lincse and the terminal program can connect. after a while (maybe 5 minutes give or take) it will no longer connect to the server...

    does this make any sense? i have the firewall disabled on the linux box... i have DNS entries for it (i thought this might be the problem, but it resolves correctly, and an entry in the host file makes no difference) the windows firewall is disabled on the clients...

    why are the clients able to connect after i ping them from the server? any clues why? the lod box is a UNIX box, but the clients are able to connect to it without a problem. it as the same application and it works...

    thanks guys,
    James
    Last edited by James Haynes; 11th December 2007, 21:06.
    its easier to beg forgiveness than ask permission.
    Give karma where karma is due...

  • #2
    Re: linux server doesnt respond to pings kinda...

    Hi,

    Few thing to know:

    1. When you say ping gives "No response" what it means? Does it remain with blank screen or you get something like "Request time out"?

    2. When you say it stops after 5 minutes? 5 minutes are after stoping the ping from Server or ping still going on...?

    3. Is any demand dial setting configured between server and user network?

    4. Check one more thing..... on client.

    check arp cache using "arp -a" for server entry during it's pinging to the server.

    once the ping stops again, check for the server entry again if it's still there or not...

    Regards,
    Kapil Sharma
    ~~~~~~~~~~~~~
    Life is too short, Enjoy It.

    Comment


    • #3
      Re: linux server doesnt respond to pings kinda...

      kapilsharma11, you had some good ideas, so thank you.

      you hit it when you said check the arp tables...

      using the packet sniffer on the firewall, i was able to see the request, but wasnt seeing the reply...

      syn...


      ... no synack.

      so, after checking the router to look at the CAM table, the server in question didnt have an entry...

      this meant the packets didnt know where to go...

      so after a little route correction and a reboot, the server actually was able to be recognized and the pings went thru.

      being that i dont understand cisco/CAT/IOS at all, i cant tell you what had to be done there to fix it, but it did involve the way the routes were setup (which was done prior to this server being operational)

      so thanks for the reply. ill pass the karma along....

      James
      its easier to beg forgiveness than ask permission.
      Give karma where karma is due...

      Comment


      • #4
        Re: linux server doesnt respond to pings kinda...

        Gr8......

        However, things should come in shape.........

        Regards,
        Kapil Sharma
        ~~~~~~~~~~~~~
        Life is too short, Enjoy It.

        Comment

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