usually this means that R4 does not have a way to reach the "next-hop" for
the R1 route. If you look at the R1 route in the BGP table, you will see
a BGP "next-hop" for this route. If that "next-hop" is not reachable (via
a directly connected interface for example), then the route will NOT go
into your IGP..........but at the same time it will sit fine in your BGP.
set "next-hop-self" on routers to avoid stuff like this.
R4 you see, has no means to get to R1 directly. When the R1 route is
learned by R3, the next-hop shows "R1". Then when the route is passed via
iBGP to R4........the next hop information is preserved..........as
R1........and since R4 doesn't know how to get to R1...........your
screwed :)
next-hop-self in the neighbor statments on R3.
Brian
On Wed, 4 Oct 2000, Sean Wu wrote:
> So what possible reason can cause this problem?
>
> I have four routers,
>
> R1 <-------> R2
> ^ ^
> | |
> | |
> | |
> v v
> R3 <-------> R4
>
> AS1: R1
> AS2: R2
> AS3: R3+R4
> IBGP between R3 and R4, EBGP between R1/R2, R2/R4, R1/R3
> Everything else looks fine, and almost symetric configuration on R1/R3 and
> R2/R4
> But R3 can see R2 in routing table and BGP table, while
> R4 doesn't see R1's ip in ip routing table, but it does see R1 in BGP table
> via two different paths
>
> Any idea?
>
> Thanks,
>
>
> Sean
>
>
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-----------------------------------------------
Brian Feeny, CCNP, CCDA [EMAIL PROTECTED]
Network Administrator
ShreveNet Inc. (ASN 11881)
**NOTE: New CCNA/CCDA List has been formed. For more information go to
http://www.groupstudy.com/list/Associates.html
_________________________________
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