Re: BGP Tricky Question

This command is done on the receiving router since it is locally
significant. Configure this on R3 since you want to alter the behavior on
R3.

On Wed, Apr 8, 2009 at 10:55 AM, Jason Alex <amr.ccie_at_gmail.com> wrote:

> Dear Andrew,
> Thanks for you info
> But i have configured the backdoor option on R1 , it has no effect
> I think if the Loopback is on R2 , i think it will works
>
> Correct me if i am wrong
>
> Regards
> Amr
>
> On Wed, Apr 8, 2009 at 4:51 PM, ALL From_NJ <all.from.nj_at_gmail.com> wrote:
>
>> 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
>>
>
>

-- 
Andrew Lee Lissitz
all.from.nj_at_gmail.com
Blogs and organic groups at http://www.ccie.net