Re: Unable to Connect to Server Ports

Discussion in 'Server Networking' started by Ace Fekay [MVP-DS, MCT], Feb 24, 2010.

  1. "W" <> wrote in message
    news:...

    > "W" <> wrote in message
    > news:D...
    >>I have a Windows 2000 box that has stopped responding to incoming TCP
    >>connections. For example, terminal services is running on port 3389.
    >>If I telnet to 3389 from the console of the affected server, that
    >>connects. If I telnet to 3389 from a remote server, that does not work.
    >>
    >> A sniffer on the affect server shows incoming TCP SYN requests, so the
    >> packets are arriving to the affected server. It really looks like the
    >> affected server either has corrupted TCP networking or has some kind of
    >> firewall running.
    >>
    >> We checked for IPSEC running, and it is not. TCP filtering is NOT
    >> turned on.
    >>
    >> We checked for any obvious firewall application running and none is.
    >>
    >> Another interesting fact here: netstat -a is taking about 20 minutes to
    >> run. Just to display the first line of the output is taking nearly five
    >> minutes. Again, this tends to suggest that something fundamental about
    >> networking is broken.
    >>
    >> Where do I begin to diagnose this and fix it?
    >>
    >> --
    >> W
    >>

    >


    > It turns out that one network interface on the affected server that uses
    > DHCP to configure its IP was enabled. The DHCP server assigned an
    > additional DNS server, which was non-existent. This DNS server took
    > priority over the correct DNS server, and no DNS requests were resolving.
    >
    > For whatever reason, this alone was breaking the ability of the box to
    > respond to incoming server connections. Once I disabled that one network
    > interface, everything started to work again.
    >
    > --
    > W
    >


    Good to know you found out the issue. FYI, for future references, we always
    recommend a single NIC on any machine, unless you use teaming.

    Also curious, if your DHCP server provided a non-existent DNS server, then
    what is occuring with the client or other machines using DHCP? They would be
    getting the incorrect info and would be causing other problems.


    --
    Ace

    This posting is provided "AS-IS" with no warranties or guarantees and
    confers no rights.

    Please reply back to the newsgroup or forum for collaboration benefit among
    responding engineers, and to help others benefit from your resolution.

    Ace Fekay, MVP, MCT, MCITP EA, MCTS Windows 2008 & Exchange 2007, MCSE &
    MCSA 2003/2000, MCSA Messaging 2003
    Microsoft Certified Trainer
    Microsoft MVP - Directory Services

    If you feel this is an urgent issue and require immediate assistance, please
    contact Microsoft PSS directly. Please check http://support.microsoft.com
    for regional support phone numbers.
     
    Ace Fekay [MVP-DS, MCT], Feb 24, 2010
    #1
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  2. "W" <> wrote in message
    news:...
    >
    >> Also curious, if your DHCP server provided a non-existent DNS server,
    >> then what is occuring with the client or other machines using DHCP? They
    >> would be getting the incorrect info and would be causing other problems.

    >
    > The DHCP server in question is some real-time telecom hardware in a test
    > lab. It's providing some kind of default value that is nonsense.
    >
    > The surprising discovery for me is that Windows would actually prioritize
    > that DNS server and make it the primary, even though the other DNS is on
    > the card with the default gateway setting.
    >
    > --
    > W


    Interesting. I 've seen that happen before, when there are two conflicting
    DHCP servers. I don't have an explanation. Unless you are saying that you
    had a static DNS entry already set?

    Ace
     
    Ace Fekay [MVP-DS, MCT], Feb 25, 2010
    #2
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  3. "W" <> wrote in message
    news:...
    > "Ace Fekay [MVP-DS, MCT]" <> wrote in
    > message news:eoJw%...
    >> "W" <> wrote in message
    >> news:...
    >>>
    >>>> Also curious, if your DHCP server provided a non-existent DNS server,
    >>>> then what is occuring with the client or other machines using DHCP?
    >>>> They would be getting the incorrect info and would be causing other
    >>>> problems.
    >>>
    >>> The DHCP server in question is some real-time telecom hardware in a test
    >>> lab. It's providing some kind of default value that is nonsense.
    >>>
    >>> The surprising discovery for me is that Windows would actually
    >>> prioritize that DNS server and make it the primary, even though the
    >>> other DNS is on the card with the default gateway setting.
    >>>
    >>> --
    >>> W

    >>
    >> Interesting. I 've seen that happen before, when there are two
    >> conflicting DHCP servers. I don't have an explanation. Unless you are
    >> saying that you had a static DNS entry already set?

    >
    > Yes, on the card configures the default gateway (static defined) we also
    > hard-code the DNS as a static entry.
    >
    > When the second ethernet card that is configured for DHCP grabbed the
    > incorrect DNS value, Windows prioritized that DNS as primary before the
    > hard coded value.
    >
    > --
    > W
    >
    >



    Out of curiosity, is this server a domain controller? And being a server,
    curious why one of the interfaces is set to DHCP?

    Ace
     
    Ace Fekay [MVP-DS, MCT], Feb 27, 2010
    #3
  4. "W" <> wrote in message news:...
    > "Ace Fekay [MVP-DS, MCT]" <> wrote in message
    > news:%...
    >> "W" <> wrote in message
    >> news:...
    >>> "Ace Fekay [MVP-DS, MCT]" <> wrote in
    >>> message news:eoJw%...
    >>>> "W" <> wrote in message
    >>>> news:...
    >>>>>
    >>>>>> Also curious, if your DHCP server provided a non-existent DNS server,
    >>>>>> then what is occuring with the client or other machines using DHCP?
    >>>>>> They would be getting the incorrect info and would be causing other
    >>>>>> problems.
    >>>>>
    >>>>> The DHCP server in question is some real-time telecom hardware in a
    >>>>> test lab. It's providing some kind of default value that is nonsense.
    >>>>>
    >>>>> The surprising discovery for me is that Windows would actually
    >>>>> prioritize that DNS server and make it the primary, even though the
    >>>>> other DNS is on the card with the default gateway setting.
    >>>>>
    >>>>> --
    >>>>> W
    >>>>
    >>>> Interesting. I 've seen that happen before, when there are two
    >>>> conflicting DHCP servers. I don't have an explanation. Unless you are
    >>>> saying that you had a static DNS entry already set?
    >>>
    >>> Yes, on the card configures the default gateway (static defined) we also
    >>> hard-code the DNS as a static entry.
    >>>
    >>> When the second ethernet card that is configured for DHCP grabbed the
    >>> incorrect DNS value, Windows prioritized that DNS as primary before the
    >>> hard coded value.
    >>>
    >>> --
    >>> W
    >>>
    >>>

    >>
    >>
    >> Out of curiosity, is this server a domain controller? And being a server,
    >> curious why one of the interfaces is set to DHCP?

    >
    > The server is not a domain controller. The server is a test computer used
    > to connect to and test telecom devices.
    >
    > The device under test is a DHCP server and it requires the computer to
    > acquire a strange IP (mask 255.255.255.252). It was just easier to put
    > that device on a dedicated segment of the test computer and set the test
    > segment to acquire the needed IP by turning on the DHCP client on the test
    > server.
    >
    > --
    > W
    >
    >



    Interesting mask. I wouldn't say it's weird, rather that mask only allows 4 IP addresses, of which 2 can actuallyy be used. I don't know what the device is, but I'm sure it has it's reasons, possibly to only have two devices only on that segment, this device and another it is communicating to.

    Ace
     
    Ace Fekay [MVP-DS, MCT], Mar 9, 2010
    #4
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