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Re: [linux] No Route to Host.

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  • Horror Vacui
    On Fri, 08 Oct 2004 12:09:46 -0400 ... That the eth0 is up doesn t have to mean much. As Michael already pointed out, whether or not the kernel knows where
    Message 1 of 8 , Oct 8, 2004
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      On Fri, 08 Oct 2004 12:09:46 -0400
      Steve wrote:

      > I am trying to figure out why a machine on my network is now saying
      > "no route to host" when I try to connect to it or connect to other
      > machines.
      > I rebooted ( unrelated to this problem ) and the problem still
      > persists. Nothing unusual shows up in dmesg. eth0 comes up when the
      > computer is started. What else can I look for?

      That the eth0 is "up" doesn't have to mean much. As Michael already
      pointed out, whether or not the kernel knows where to send packets
      depends on its routing tables, which are built based on your network
      card configuration. When the kernel doesn't know that, you get the "no
      route to host". This can occur for various reasons - when a card is up,
      but is assigned no IP address (it shouldn't show up in the output of
      ifconfig then, but occasionally it does), or it's assigned a bad IP
      address (wrong subnet, wrong netmask)...

      So check whether the IP address is the one you think should be assigned
      to the NIC, then check whether the route for it is what you think it
      should be, and you'll know what the problem is. But before you do all
      that, check whether the physical link is ok. That's a gladly overlooked
      cause of many networking problems.

      Cheers

      --
      Horror Vacui

      Registered Linux user #257714

      Go get yourself... counted: http://counter.li.org/
      - and keep following the GNU.
    • Steve
      ... I have checked that as well. All the entries taht were tehre before this happened are still there. The no route to host came on out of the blue. I
      Message 2 of 8 , Oct 8, 2004
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        Michael Kjorling wrote:
        > 2004-10-08 12:09, spatz@... wrote in <4166BBCA.8040906@...>:
        >
        >>>I am trying to figure out why a machine on my network is now saying "no
        >>>route to host" when I try to connect to it or connect to other machines.
        >
        >
        > Missing/incorrect kernel IP routing table. /sbin/route is your friend.
        >

        I have checked that as well. All the entries taht were tehre before
        this happened are still there. The no route to host came on out of the
        blue. I checked the connections at the switch, and the LEDs for that PC
        flash on then off ( when I was trying to ping the other PC on the network.)

        --
        http://s87365085.onlinehome.us/
      • Vijaykumar V K
        ... You can probably try to ping to other machines in your netwrok..if it is pinging properly, then you need to probably check your firewall settings in your
        Message 3 of 8 , Oct 8, 2004
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          On Fri, 08 Oct 2004 23:57:41 -0400, Steve <spatz@...> wrote:
          >
          >
          >
          > I have checked that as well. All the entries taht were tehre before
          > this happened are still there. The no route to host came on out of the
          > blue. I checked the connections at the switch, and the LEDs for that PC
          > flash on then off ( when I was trying to ping the other PC on the network.)
          >

          You can probably try to ping to other machines in your
          netwrok..if it is pinging properly, then you need to probably check
          your firewall settings in your machine using iptables -L..

          Hope that will work ..:-)

          --
          Regards,
          Vijay
        • Steve
          ... The iptables entires were unchanged as well. -- http://s87365085.onlinehome.us/
          Message 4 of 8 , Oct 9, 2004
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            Vijaykumar V K wrote:
            > On Fri, 08 Oct 2004 23:57:41 -0400, Steve <spatz@...> wrote:
            >
            >>
            >>
            >>I have checked that as well. All the entries taht were tehre before
            >>this happened are still there. The no route to host came on out of the
            >>blue. I checked the connections at the switch, and the LEDs for that PC
            >>flash on then off ( when I was trying to ping the other PC on the network.)
            >>
            >
            >
            > You can probably try to ping to other machines in your
            > netwrok..if it is pinging properly, then you need to probably check
            > your firewall settings in your machine using iptables -L..
            >
            > Hope that will work ..:-)
            >

            The iptables entires were unchanged as well.

            --
            http://s87365085.onlinehome.us/
          • Wolf Dreamer
            (1) turn iptables off. (2) manually set a default route and see if that works. That would be the first steps I would take. if it does then make sure your
            Message 5 of 8 , Oct 10, 2004
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              (1) turn iptables off.

              (2) manually set a default route and see if that works.

              That would be the first steps I would take. if it does then make sure your
              default setup has the correct default route.
            • Steve
              ... It turns out it was the cable. But not the connection to the ailing machine, but the other machine on the network. I had just made sure it was plugged
              Message 6 of 8 , Oct 10, 2004
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                Wolf Dreamer wrote:
                > (1) turn iptables off.
                >
                > (2) manually set a default route and see if that works.
                >
                > That would be the first steps I would take. if it does then make sure your
                > default setup has the correct default route.


                It turns out it was the cable. But not the connection to the ailing
                machine, but the other machine on the network. I had just made sure it
                was plugged in, but after removing it and reconnecting, the network came
                back to normal.


                --
                http://s87365085.onlinehome.us/
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