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" <ppetit@synet.fr> To: <nanog@merit.edu> Subject: IBGP problem concerning more specific routes Date: Tue, 2 Dec 1997 21:03:53 +0100 Reply-to: ppetit@synet.fr

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: ppetit@synet.fr FRANCE http://www.synet.fr