route preference - ospf or static.

Discussion in 'Cisco' started by news8080@yahoo.com, Oct 12, 2006.

  1. Guest

    As I understand it, connected routes have 1 weight and OSPF routes have
    110 weight. Now what happens in a case where I have a /24 ospf route
    (e2) being learned on a device and I put a static route that is /23
    (which should cover that /24 route that I learn via ospf) what takes
    over then?

    I have this setup but can't really screw with production environment to
    try this or I'd do that before posting.

    anyone?
     
    , Oct 12, 2006
    #1
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  2. John Agosta Guest

    <> wrote in message
    news:...
    > As I understand it, connected routes have 1 weight and OSPF routes have
    > 110 weight. Now what happens in a case where I have a /24 ospf route
    > (e2) being learned on a device and I put a static route that is /23
    > (which should cover that /24 route that I learn via ospf) what takes
    > over then?
    >
    > I have this setup but can't really screw with production environment to
    > try this or I'd do that before posting.
    >
    > anyone?
    >



    Longest mask length ALWAYS wins.
     
    John Agosta, Oct 13, 2006
    #2
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  3. Guest

    Thanks, is there any cisco documentation link you can send me on that?

    John Agosta wrote:
    > <> wrote in message
    > news:...
    > > As I understand it, connected routes have 1 weight and OSPF routes have
    > > 110 weight. Now what happens in a case where I have a /24 ospf route
    > > (e2) being learned on a device and I put a static route that is /23
    > > (which should cover that /24 route that I learn via ospf) what takes
    > > over then?
    > >
    > > I have this setup but can't really screw with production environment to
    > > try this or I'd do that before posting.
    > >
    > > anyone?
    > >

    >
    >
    > Longest mask length ALWAYS wins.
     
    , Oct 13, 2006
    #3
  4. Guest

    wrote:
    > Thanks, is there any cisco documentation link you can send me on that?


    Who needs Cisco documentation? That rule is one of the fundamental
    rules of IP routing. Look it up in any book on routing.
     
    , Oct 13, 2006
    #4
  5. Scooby Guest

    <> wrote in message
    news:...
    >
    > wrote:
    >> Thanks, is there any cisco documentation link you can send me on that?

    >
    > Who needs Cisco documentation? That rule is one of the fundamental
    > rules of IP routing. Look it up in any book on routing.
    >


    Absolutely correct. But, just in case the OP is still looking...

    http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094823.shtml

    BTW - that took all of about 2 minutes to search Cisco's site and read the
    key points of the article.
     
    Scooby, Oct 13, 2006
    #5
  6. John Agosta Guest

    google administrative distance site:cisco.com route selection
    site:cisco.com






    <> wrote in message
    news:...
    >
    > Thanks, is there any cisco documentation link you can send me on that?
    >
    > John Agosta wrote:
    >> <> wrote in message
    >> news:...
    >> > As I understand it, connected routes have 1 weight and OSPF routes have
    >> > 110 weight. Now what happens in a case where I have a /24 ospf route
    >> > (e2) being learned on a device and I put a static route that is /23
    >> > (which should cover that /24 route that I learn via ospf) what takes
    >> > over then?
    >> >
    >> > I have this setup but can't really screw with production environment to
    >> > try this or I'd do that before posting.
    >> >
    >> > anyone?
    >> >

    >>
    >>
    >> Longest mask length ALWAYS wins.

    >
     
    John Agosta, Oct 13, 2006
    #6
  7. Sam Wilson Guest

    In article <>,
    wrote:

    > wrote:
    > > Thanks, is there any cisco documentation link you can send me on that?

    >
    > Who needs Cisco documentation? That rule is one of the fundamental
    > rules of IP routing. Look it up in any book on routing.


    It's not just that, it's that we're comparing two different things. The
    administrative distance (the weight the OP refers to) is used to decide
    which routing protocol to take a routing table entry from - if the same
    prefix (same value, same prefix length) is learned in two different
    protocols the better admin distance is chosen. Once routes are
    installed in the table then longest match decides which entry is used to
    route the packet. Prefixes of two different lengths don't conflict when
    it comes to admin distance.

    Sam
     
    Sam Wilson, Oct 13, 2006
    #7
  8. Manohar Guest

    I agree with Sam. During the Route selection process, longest prefix
    matched is prefered. If the prefix length is same then admin distance
    is compared.

    Regards

    Manohar

    wrote:
    > As I understand it, connected routes have 1 weight and OSPF routes have
    > 110 weight. Now what happens in a case where I have a /24 ospf route
    > (e2) being learned on a device and I put a static route that is /23
    > (which should cover that /24 route that I learn via ospf) what takes
    > over then?
    >
    > I have this setup but can't really screw with production environment to
    > try this or I'd do that before posting.
    >
    > anyone?
     
    Manohar, Oct 14, 2006
    #8
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