thanks I understand now , but how there is one more
thing that needs u to further clarify and that is the
first soluion that you mention , I dont quite
understand why it will solve the problem
appreciate if you can elaborate
thanks
suaveguru
--- Peter Van Oene <[EMAIL PROTECTED]> wrote:
> When BGP routers learn routes via BGP, they learn
> two key pieces of information; A destination prefix,
> and a next hop address. Within an AS, BGP routers
> communicate with IBGP. Within the AS however, the
> next hop address for each prefix is by default not
> modified. That means that all IBGP routers within
> an AS will maintain a consistent view of the
> external world.
>
> However, consider the following.
>
> R1 AS1 <-------> R2 AS2 <-------R2 AS2
> EBGP IBGP
>
> Consider that R1 advertises prefix 10/8 into AS2.
> R2 will learn this 10/8 address and the
> corresponding next hop address. In this case, lets
> say that 11/8 is the subnet between R1 and R2 and
> R1's uses 11.0.0.1 and R2 uses 11.0.0.2. Hence, R2
> will publish 10/8 with a next hop of 11.0.0.1 in its
> routing table.
>
> R2 will then advertise 10/8 via IBGP to R2 with the
> next hop of 11.0.0.1. However, as 11/8 is an
> external point to point link and may not be a subnet
> that R2 is aware of. If this is the case, R2 will
> not be able to resolve a route toward 11/8 and thus
> will be unable to post the route due to the rules of
> BGP.
>
> Two solutions exist to solve this problem (well two
> pop into my mind). The first way would be to have
> R2 advertise the external link (11/8 in this case)
> into the AS so that all IBGP routers will learn it.
> This however increases the size and complexity of
> the IGP within the AS.
>
> The second option is to have R2 replace the next hop
> address with his own address. Naturally, his own
> address will be known throughout the AS (BGP depends
> on TCP so this has to be the case) and thus when R2
> receives the 10/8 advertisement, it will see R2's
> interface as the next hop and thus be able to
> resolve the bgp next hop and post the route.
>
> I hope this makes sense :)
>
> Pete
>
>
>
>
> *********** REPLY SEPARATOR ***********
>
> On 11/3/2000 at 11:58 AM suaveguru wrote:
>
> >hi ,
> >
> >Anyone knows what does next-hop-self in bgp means
> >please explain to me
> >
> >thanks
> >
> >suaveguru
> >
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