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4714 Views 5 Replies Latest reply: Mar 13, 2009 2:24 PM by smirk.com RSS

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Split Horizon

Mar 12, 2009 3:12 PM

smirk.com 10 posts since
Sep 13, 2008

Hi can anybody tell me what is split horizon with a simple example thankyou i am getting confused with it

  • Paul Stewart  -  CCIE Security 7,568 posts since
    Jul 18, 2008
    Currently Being Moderated
    1. Mar 12, 2009 3:39 PM (in response to smirk.com)
    Re: Split Horizon

     

    If you are sitting around quietly with a group of people. If one person says something interesting. Do you repeat it to the group, or assume that the rest of the group heard it because they were all sitting in equal proximity to the person that made the original statement? Split horizon would be the assumption that everyone else heard the statement and you have no need to repeat it.

     

     

     

     

     

    From a network perspective it is very similar. If a router hears of a route, it may repeat those routes out another interface, but not the interface it heard the routes from. This is because if there are multiple routers, directly connected out that single interface, the assumption can be made that they all have equal access to one another. At least that is the assumption.

     

     

     

     

     

    There are situations that it is not true and split horizon should be disabled. If a route is received on an interface, the router "typically" should not send that route out the same interface. The route should be sent out the other interfaces.

     

     

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  • Armen 247 posts since
    Jul 7, 2008
    Currently Being Moderated
    2. Mar 12, 2009 3:39 PM (in response to smirk.com)
    Re: Split Horizon

    Basicly, when R1 receives a route from R2, R1 will not advertise the same route back to R2 .

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  • shanekillian 230 posts since
    Aug 18, 2008
    Currently Being Moderated
    3. Mar 12, 2009 5:21 PM (in response to smirk.com)
    Re: Split Horizon

     

    Hi there,

     

     

    I think its fair to say that Paul and Armen have descibed Split Horizon in a clear and concise way.

     

     

    Just to add to what they have said above, you may find this Wiki link worthwhile:

     

     

    http://en.wikipedia.org/wiki/Split_horizon

     

     

     

     

     

    Wikipedia ... the greatest thing since sliced bread... and TCP/IP

     

     

     

     

     

     

     

     

    All the best,

     

     

     

     

     

    Shane

     

     

     

     

     

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  • Scott Morris - CCDE/4xCCIE/2xJNCIE 8,426 posts since
    Oct 7, 2008
    Currently Being Moderated
    4. Mar 12, 2009 6:55 PM (in response to shanekillian)
    Re: Split Horizon

    And MQC/NBAR.

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