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Thread: Linux router question

  1. #11
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    Anyways isnt it possible that some windows machine transmitting the rip for its subnet? or some other factor like one machine having an ip address on that subnet?, its a long shot but those ips are usually used by windows by default.
    I have been testing with static routes. I don't think that rip is enabled but I will check.

    So, what happens if you unplug eth1 and boot the box?
    I will test this.

    Linux doesnt create static routes by itself,
    How do the static routes get created?

  2. #12
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    Anyways isnt it possible that some windows machine transmitting the rip for its subnet?
    Only if the Windows machine is RIP router.

    Also, when a machine has 169.254 ip address there is no default gateway, just the IP and subnet mask.

    its a long shot but those ips are usually used by windows by default.
    I have seen Linux machine issue the 169.254 ip address if it does not find the DHCP server.
    Last edited by juba; Jan 8, 2006 at 10:24 AM.

  3. #13
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    So, what happens if you unplug eth1 and boot the box?
    The address gets attached to eth0.

    I have checked 2 other Linux servers on my network and both have this route.

    At any rate, the router is working as it should. I have added the change to ip_forward in the /etc/rc.local file so it is applied when the machine starts up.

    I will try Quagga and the dynamic routes next.

  4. #14
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    Automatic Private IP Addressing.

    Some DHCP clients will default to 169.254.0.1 through 169.254.255.254 when the client in question cannot find a proper DHCP SERVER response.

    So the client will automatically configure itself/NIC to use anyone of these addresses until the DHCP SERVER comes online again or not.

    These IP's are to be a range of IP specially set aside for this feature.

    In short it is creating a network without causing conflict.

    How this is achieved is the DHCP client will attempt to ARP addressess in the IP range aforementioned and it will randomly choose from the said range but exclude any address that answers from the ARP query.

    Understand ?

    Think of it as a crude way of automatically network configuration.


    APIPA configuration in /etc/name_of _your_nic/dhcp_config_file

    # Try DHCP first if that fails then fallback to APIPA
    config_eth0=( "dhcp" )
    fallback_eth0=( "apipa" )
    Look in your DHCP conf file for that.

    You can force it to use APIPA with

    config_eth0=( "apipa" )
    Which is what happens to most people.

    My SuSE systems loves to do this with my wireless NIC which I do not have a connection for.
    Last edited by Gillion; Jan 8, 2006 at 10:22 PM.
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  5. #15
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    wow, i am forever amazed at gillions range of troubleshooting knowledge. who said command line and config files werent good, lol
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  6. #16
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    Some DHCP clients will default to 169.254.0.1 through 169.254.255.254 when the client in question cannot find a proper DHCP SERVER response.
    Understand ?

    Jamrock:
    On Windows I see a 169 address when the workstation cannot connect to dhcp to get an address. The router is using fixed i.p. addresses so this should not be an issue.
    Juba:
    I have seen Linux machine issue the 169.254 ip address if it does not find the DHCP server.
    Please check the routing table on your Linux boxes to see if there is a route for the 169 subnet. I see it on all my Linux servers and all have fixed i.p. addresses that work.

    You can check your route table by typing

    route -n
    Last edited by jamrock; Jan 9, 2006 at 08:30 AM.

  7. #17
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    What distro do you use jamrock? Check the network init scripts.

    I dont have any routes to any 169.254/16 networks on any of my linux
    boxes with static or dhcp client assigned ip addresses. The distro I use
    is slackware and the network init scripts are very bare and to the point

    Something like this: http://www.etse.urv.es/~larinyo/Ethe.../rc.inet1.html

    Thats why I said set out the traps for the elves. There is some init script,
    dhcp client, or routing daemon thats setting that route on your boxes heh

  8. #18
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    Quote Originally Posted by jamrock
    I have two subnets, 192.168.1.0 and 192.168.0.0. I would expect to see routing entries for these two subnets.

    From what I have read, when network cards are configured, routes are automatically added to the routing table for their subnets.

    Not sure how the 169.254.0.0 got there. If I delete it and restart the machine it gets re-created.

    Juba, Gillion, anyone?
    I think that is tha ip range Windows uses when it cannot locate a dhcp server....Not sure how that got on your router though...
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  9. #19
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    What distro do you use jamrock? Check the network init scripts.

    I dont have any routes to any 169.254/16 networks on any of my linux
    boxes with static or dhcp client assigned ip addresses. The distro I use
    is slackware and the network init scripts are very bare and to the point
    Slackware and Debian are much different from the commercial distros. I am curious to see what Suse and Mandriva have.

    I use CentOS, a Red Hat clone.

  10. #20
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    I found this doing some googling.

    http://www.redhat.com/archives/fedor.../msg03576.html

    Seems to be the norm on Red Hat distro since RH9. I don't have a Red Hat or CentOS installed right now, but I will do an install and let you know.

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