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Linux Networking

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  • Helios
    Hello! I am having a problem , please help me out. I created a network for 10 systems in my lab, running RHEL-3 as a OS on all the systems, assign all the
    Message 1 of 3 , Dec 4, 2009
      Hello!

      I am having a problem , please help me out.

      I created a network for 10 systems in my lab, running RHEL-3 as a OS on all the systems, assign all the systems with their respective IP-addresses in the same network [Class C], out of these 10 systems one of them is having 2 ethernet devices, one device is having the IP from the same network but the other device is configured in a Class B network
      when i try to ping this system from the other nine, it does not. How can i make it ping.

      thankyou,


      Helios
    • J
      ... Most likely, on that one machine, you either have the NICs configured backwards or improperly. E.G. the one that connects to your class B network is
      Message 2 of 3 , Dec 4, 2009
        On Fri, Dec 4, 2009 at 10:56, Helios <syed.khawar@...> wrote:

        > I am having a problem , please help me out.
        >
        > I created a network for 10 systems in my lab, running RHEL-3 as a OS on all the systems, assign all the
        > systems with their respective IP-addresses in the same network [Class C], out of these 10 systems one of
        > them is having 2 ethernet devices, one device is having the IP from the same network but the other device is
        > configured in a Class B network
        > when i try to ping this system from the other nine, it does not. How can i make it ping.

        Most likely, on that one machine, you either have the NICs configured
        backwards or improperly.

        E.G. the one that connects to your class B network is plugged into
        your Class C network, and vice versa.

        Can you, from the machine with two NICs, ping each of the other 9
        machines? You can specify which NIC the ping leaves from like so:

        ping -i ethX 192.168.1.1

        where X is the number assigned to the eth device in question.

        Either that, or if that machine is acting like some sort of gateway or
        router, you have some problems with your firewall, if you're running
        it.

        If you have the firewall turned on, run as root: "iptables -F" and
        "service iptables stop" THEN try pinging that machine from your other
        lab machines. If the pings work, then you know you need to revise
        your firewall rules.

        Also, if you are using RHEL AND you're using the default RHEL firewall
        settings, this is not surprising, as the default RHEL firewall
        settings tend to be... shall we say overzealous in what they block.

        Cheers,

        Jeff
        --

        Ogden Nash  - "The trouble with a kitten is that when it grows up,
        it's always a cat."
      • Dan
        Jeff, Hope you don t mind if I add my comments...  --- On Fri, 12/4/09, J wrote: From: J Subject: Re:
        Message 3 of 3 , Dec 4, 2009
          Jeff, Hope you don't mind if I add my comments...

           --- On Fri, 12/4/09, J <dreadpiratejeff@...> wrote:

          From: J <dreadpiratejeff@...>
          Subject: Re: [redhat] Linux Networking
          To: redhat@yahoogroups.com
          Date: Friday, December 4, 2009, 12:00 PM







           









          On Fri, Dec 4, 2009 at 10:56, Helios <syed.khawar@ yahoo.com> wrote:



          First question:

          Why are you running RHEL 3.....

          if it is because you have the CD, download CENTOS 5.3 (RHEL5/R3) or better yet the new version of Fedora.
          Created tells me that you aquired the CD's and installed them.  I cannot think of a business reason to install RHEL3 on a fresh network.  But no support, means no updates, so there are security flaws and application flaws.the ISO images are online for free.....

          > I am having a problem , please help me out.

          >

          > I created a network for 10 systems in my lab, running RHEL-3 as a OS on all the systems, assign all the

          > systems with their respective IP-addresses in the same network [Class C], out of these 10 systems one of

          > them is having 2 ethernet devices, one device is having the IP from the same network but the other device is

          > configured in a Class B network

          > when i try to ping this system from the other nine, it does not. How can i make it ping.Ping the IP address for the machine, see if it can see itself.Then ping the switch server, it is usually the IP with the last octect a 1  sometimes a 254, and when you have problematic network engineers they use something else.Do an ifconfig -a as root.ifup eth0   (eth zero) in order to make sure the interface is up.
          Make sure the interface gives you an IP address and has "UP" you may need to do an Most likely, on that one machine, you either have the NICs configured

          backwards or improperly.



          E.G. the one that connects to your class B network is plugged into

          your Class C network, and vice versa.



          Can you, from the machine with two NICs, ping each of the other 9

          machines? You can specify which NIC the ping leaves from like so:



          ping -i ethX 192.168.1.1



          where X is the number assigned to the eth device in question.



          Either that, or if that machine is acting like some sort of gateway or

          router, you have some problems with your firewall, if you're running

          it.



          If you have the firewall turned on, run as root: "iptables -F" and

          "service iptables stop" THEN try pinging that machine from your other

          lab machines. If the pings work, then you know you need to revise

          your firewall rules.



          Also, if you are using RHEL AND you're using the default RHEL firewall

          settings, this is not surprising, as the default RHEL firewall

          settings tend to be... shall we say overzealous in what they block.



          Cheers,



          Jeff

          --



          Ogden Nash  - "The trouble with a kitten is that when it grows up,

          it's always a cat."




















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