North American Network Operators Group

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Re: IBGP problem concerning more specific routes

  • From: Vincent J. Bono
  • Date: Fri Dec 05 08:31:58 1997

Routes heard from EBGP only travel one hop into your network when 
exported via IBGP.  But, this should meet that criteria. Have you 
done anything with localpref values or weights?  It may be that R2 is 
ignoring the specificity of the /24 in deference to the AS Path and 
Local AS number of the /16.   

-v

> From:          "Pascal Petit - SYNET" <[email protected]>
> To:            <[email protected]>
> Subject:       IBGP problem concerning more specific routes
> Date:          Tue, 2 Dec 1997 21:03:53 +0100
> Reply-to:      [email protected]

> Here is an amusing BGP problem :
> 
> 
>    Wild Wolrd-----------R1--------------R2------Our Networks
>  
>  There is an IBGP sesion running between R1 and R2. R2 advertises route
>  194.214.0.0/16 to R1. In our block there is a class C used by one of our
>  customer  which is not directly connected to our network. This customer
>  advertises its class C to the Wild World via its own ISP.
>  
>  R1 receives the 194.214.253.0/24 advertisement from the Wild World, it
>  stores it in its routing table; however R2 never takes it into account :
>  its routing table only mentions 194.214.0.0/16 , it doesn't mention the
>  more specific routing entry 194.214.253.0/24.
> 
>  Our Networks cannot get to 194.214.253.0/24. Is it a feature of IBGP ??
>  
>  Thanks for any help,
> 
> Pascal
>  
>  
>  ------------------------------------------------------------------------
> Pascal Petit
>  SYNET                                          tel:        33 1 4696 0040
>  74, rue Roque de Fillol                    fax:       33 1 4696 0041
>  92800 Puteaux                               email:    [email protected]
>  FRANCE                                         http://www.synet.fr   
> 
>