Re: BGP Tricky Question

Hello Jason,

When you are learning a route via eBGP and and OSPF, the ADs are 20 and
110. 20 is better than 110 ...

You can not change the AD ... in this case, you need to tell BGP that the
IGP route should be preferred.

This link should assist (watch for the ugly word wrap):

http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_bgp4.html#wp1012431

From this link:
*Usage Guidelines * **

* A backdoor network is assigned an administrative distance of 200. The
objective is to make Interior Gateway Protocol (IGP) learned routes
preferred. A backdoor network is treated as a local network, except that it
is not advertised. A network that is marked as a back door is not sourced by
the local router, but should be learned from external neighbors. The BGP
best path selection algorithm does not change when a network is configured
as a back door*
This was one of those topics I had to lab up to learn. Once I labbed it, it
made sense to me. HTH and have a great day,

Andrew Lee Lissitz

On Wed, Apr 8, 2009 at 10:30 AM, Jason Alex <amr.ccie_at_gmail.com> wrote:

> Dear All,
> The Setup is as follows
>
> R1(s0/0)-----------OSPF Area 0-----------(S0/0)R2(fa0/0)---------OSPF Area
> 1---------------(fa0/0)R3
>
> R1 is in BGP AS 10
> R2 is in BGP AS 10
> R3 is in BGP AS 20
>
> R2 peers with R1 & R3
>
> *The Question Says that:*
> Configure Loopback 40 on R1 (40.40.40.40/32) and advertise it to R2 via
> both
> OSPF & BGP
> Make sure that R3 Sees Loopback 40 of R1 as O IA route with AD 110 , and
> the
> route must also appears on R3's BGP table
> You must not use the distance command
>
> Any ideas how to solve this question without using the distance command
>
> Regards
>
>
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-- 
Andrew Lee Lissitz
all.from.nj_at_gmail.com
Blogs and organic groups at http://www.ccie.net