Problem routing to a cisco loopback address of *.*.*.255

Discussion in 'Cisco' started by Wazza, Dec 1, 2003.

  1. Wazza

    Wazza Guest

    Anyone come across a problem routing from windoes 2000 to a cisco loopback
    address od *.*.*.255, Windows thinks that it is a broadcast address and
    refuses to route it.

    TIA

    Wazza
     
    Wazza, Dec 1, 2003
    #1
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  2. Wazza

    Ivan Guest

    "Wazza" <> wrote in message
    news:Xns944476BF073CEwazza@132.146.191.33...
    > Anyone come across a problem routing from windoes 2000 to a cisco loopback
    > address od *.*.*.255, Windows thinks that it is a broadcast address and
    > refuses to route it.
    >


    Which netmask do you use on loopback? If it's not a /32, you shouldn't use
    that address...

    Ivan
     
    Ivan, Dec 1, 2003
    #2
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  3. Wazza

    Wazza Guest

    "Ivan" <> scribbled in
    news:bqfff5$21ngvr$-berlin.de:

    > "Wazza" <> wrote in message
    > news:Xns944476BF073CEwazza@132.146.191.33...
    >> Anyone come across a problem routing from windoes 2000 to a cisco
    >> loopback address od *.*.*.255, Windows thinks that it is a broadcast
    >> address and refuses to route it.
    >>

    >
    > Which netmask do you use on loopback? If it's not a /32, you shouldn't
    > use that address...
    >
    > Ivan
    >
    >
    >


    I will try and make this clearer.

    There is a router on the network with a loopback address of "*.*.*.255",
    i can ping that ok from unix servers, but win2k servers wont. I can ping
    "*.*.*.254" from both unix and win2k. Win2k seems to be making a decision
    not to allow any traffic to "*.*.*.255". Is this "special" as far as
    windows is concerned? Is there a setting i can change to allow traffic to
    route to *.*.*.255?

    Cheers

    Wazza
     
    Wazza, Dec 1, 2003
    #3
  4. I would configure that loopback address to be something else, anything but *.*.*.0 or *.*.*.255.
    Then, as Ivan said, put a /32 (255.255.255.255) mask on it.. Make it a different subnet than the
    network your Unix and Win2k boxes are on.. As long as they have the correct default gateway, they
    should be able to hit it.. I've done this same setup at home...

    I would bet your successful pings from your Unix box aren't getting to your router's loopback, they
    are getting to the broadcast IP for your subnet, with success! ;-) And your Win2K box is actually
    being wiser in this case, saying "Hey, why would I want to ping a broadcast IP anyway??" ;-)

    In comp.dcom.sys.cisco Wazza <> wrote:
    : "Ivan" <> scribbled in
    : news:bqfff5$21ngvr$-berlin.de:

    :> "Wazza" <> wrote in message
    :> news:Xns944476BF073CEwazza@132.146.191.33...
    :>> Anyone come across a problem routing from windoes 2000 to a cisco
    :>> loopback address od *.*.*.255, Windows thinks that it is a broadcast
    :>> address and refuses to route it.
    :>>
    :>
    :> Which netmask do you use on loopback? If it's not a /32, you shouldn't
    :> use that address...
    :>
    :> Ivan
    :>
    :>
    :>

    : I will try and make this clearer.

    : There is a router on the network with a loopback address of "*.*.*.255",
    : i can ping that ok from unix servers, but win2k servers wont. I can ping
    : "*.*.*.254" from both unix and win2k. Win2k seems to be making a decision
    : not to allow any traffic to "*.*.*.255". Is this "special" as far as
    : windows is concerned? Is there a setting i can change to allow traffic to
    : route to *.*.*.255?

    : Cheers

    : Wazza
     
    Mike S. Whitlow, Dec 1, 2003
    #4
  5. Wazza

    Rod Dorman Guest

    In article <Xns94448C173BB57wazza@132.146.191.33>,
    Wazza <> wrote:
    >There is a router on the network with a loopback address of "*.*.*.255",
    >i can ping that ok from unix servers, but win2k servers wont. I can ping
    >"*.*.*.254" from both unix and win2k. Win2k seems to be making a decision
    >not to allow any traffic to "*.*.*.255". Is this "special" as far as
    >windows is concerned? Is there a setting i can change to allow traffic to
    >route to *.*.*.255?


    Is there anything in the configuration that would make it think
    "*.*.*.255" is in a /24 network?

    --
    -- Rod --
    rodd(at)polylogics(dot)com
     
    Rod Dorman, Dec 1, 2003
    #5
  6. Wazza

    mikester Guest

    (Rod Dorman) wrote in message news:<bqg5s4$5ln$>...
    > In article <Xns94448C173BB57wazza@132.146.191.33>,
    > Wazza <> wrote:
    > >There is a router on the network with a loopback address of "*.*.*.255",
    > >i can ping that ok from unix servers, but win2k servers wont. I can ping
    > >"*.*.*.254" from both unix and win2k. Win2k seems to be making a decision
    > >not to allow any traffic to "*.*.*.255". Is this "special" as far as
    > >windows is concerned? Is there a setting i can change to allow traffic to
    > >route to *.*.*.255?

    >
    > Is there anything in the configuration that would make it think
    > "*.*.*.255" is in a /24 network?


    We're grasping at straws here, you haven't provided enough information
    to get any concise help.

    I'll grasp anyway though...

    To my knowledge Unix and Windows do not stop you from pinging the
    broadcast ip address unless that machine (Unix or windows) knows
    specifically that the ip you are trying to ping is a broadcast ip. The
    only way that would really be is if the server were physically on that
    network. For example, I have a redhat server on 10.0.0.0 /24. The
    broadcast on that network is 10.0.0.255 and if I try to ping it I must
    put in the "-b" flag to indicate that yes I do want to ping the
    broadcast ( I don't think windows does this or cares if you ping the
    broadcast). In such a case I would get a response back from every
    device on that subnet. Well, lets look at another example. 10.0.0.0
    /23, the broadcast there would be 10.0.1.255 not 10.0.0.255.
    10.0.0.255 would be a perfectly valid ip address to use as it is in
    the middle of the subnet. As would be the case if you used 10.0.0.0/32
    as a loopback address - there should be no problem with that as it is
    a perfectly valid single ip subnet per the VLSM rules. Just the same,
    as stated earlier by someone else - *.*.*.255/32 is a perfectly valid
    single ip subnet that would be just fine to use and route as a
    loopback address.

    Are the UNIX servers you're speaking of on the same subnet as your
    windows 2k servers?

    What is the exact configuration of that loopback and it's
    corresponding routing entry?

    for example
    loopback0
    ip address *.*.*.255 255.255.255.255 ?

    router ospf 1 <--assuming ospf
    network *.*.*.255 0.0.0.0 area 0?

    Also, showing a routing entry from a neighbor router might help too -
    maybe you have a routing issue.

    Also, if the UNIX and W2K servers are on the same subnet - compare
    their configurations - make sure they are itentical (with the
    exception of the actual IP assigned to each of course).

    Good luck.

    The Mikester
     
    mikester, Dec 2, 2003
    #6
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