Re: BGP conditional adv??

From: Tolulope Ogunsina <togunsina_at_gmail.com>
Date: Thu, 25 Feb 2010 16:48:51 +0100

Right on point!

Cheers!

On 2/25/10, Ivan Hrvatska <ivanzghr_at_gmail.com> wrote:
> OK. I think I get it. Correct me if I'm wrong:
>
> if my agg route has {100,300} which are AS numbers of R1 and R3, R1
> and R3 will discard that agg prefix cause they see it's own AS number.
> When I do this, on the R2 which is originator of agg rute:
>
> ip as-patch acl 1 per ^300$
> route-map XXX
> match as-patch 1
> router bgp 200
> agg-add 3.1.0.0 255.255.240.0 summ-only as-set adv-map XXX
>
> I'm actually permitting only ASN 300 in AS_PATH, so R1 will process
> agg route and install it in BGP table cause it doesn't see it's AS
> number. R3 will discard it. Is this correct? Is this the functionality
> of adv-map with aggregation?
>
> Regards
>
> On Thu, Feb 25, 2010 at 2:47 PM, Tolulope Ogunsina <togunsina_at_gmail.com>
> wrote:
>> Hi,
>> The advertise-map in aggregate address command is different from the
>> advertise map in conditional advertisements.
>> In aggregate address, the advertise-map argument is the "Name of the
>> route map used to select the routes to create AS_SET origin
>> communities"
>>
>> With that said, I do NOT fully understand the scenario you're
>> describing. Please shed some more light.
>>
>> On 2/25/10, Ivan Hrvatska <ivanzghr_at_gmail.com> wrote:
>>> Oh, yea. I didn't read carefully :) First bullet will be done by
>>> default. Third bullet will also be done by default. So, the second
>>> bullet is actually going through the task on reverse way. If 1.0.0.0
>>> is DOWN, nothing is going to be advertised, and if it is UP, only
>>> 2.0.0.0 will be advertised. OK. I get it. I was confused by the way
>>> the task is given.
>>>
>>> As I go further through the BGP i have one more issue.
>>> One task:
>>>
>>> R1------R2-------R3
>>>
>>> R3 has couple of specific nets which are aggregated by R2. R1 only
>>> gets aggregate prefix without atomic-agg attribute (summary-only and
>>> as-set is used). The aggregation should be configured such that R1 in
>>> AS 100 is the only AS that recivies agg route. R3 or future peer
>>> neighbors should NOT receive the agg route.
>>> Solution:
>>> ip as-path access-list 1 permit ^300$
>>> route-map TST per 10
>>> match as-path 1
>>> agg 3.1.0.0 255.255.240.0 as-set summ-only adv-map TST
>>>
>>> First, I planned to solve this task with community no-export. R2 sets
>>> that comm to the agg route and send it to R1.
>>> I don't het what this route-map exactly does in this case? as-path acl
>>> matches prefixes originated in AS 300. What else in combination with
>>> agg-add command?
>>>
>>> regards
>>>
>>> On Thu, Feb 25, 2010 at 11:20 AM, Tolulope Ogunsina <togunsina_at_gmail.com>
>>> wrote:
>>>> The solution means advertise 2.0.0.0 if (and only if) 1.0.0.0 exists
>>>> which also means if 1.0.0.0 does NOT exist, do NOT advertise 2.0.0.0.
>>>>
>>>> On 2/25/10, Ivan Hrvatska <ivanzghr_at_gmail.com> wrote:
>>>>> Yes, that is true. But shouldn't solution be: if 1.0.0.0/8 is DOWN, do
>>>>> NOT advertise 2.0.0.0:
>>>>>
>>>>> in solution in route-map EXIST you are matching 1.0.0.0, which means,
>>>>> if 1.0.0.0 exist in RIB, advertise what you permit in route-map ADV,
>>>>> and in route-map ADV you permit 2.0.0.0. That's what is confusing to
>>>>> me.
>>>>>
>>>>> On Thu, Feb 25, 2010 at 9:32 AM, Tolulope Ogunsina
>>>>> <togunsina_at_gmail.com>
>>>>> wrote:
>>>>>> Hi Ivan,
>>>>>> From the question,
>>>>>>
>>>>>> - if both nets 1.0.0.0 and 2.0.0.0 are up, R1 should advertise them
>>>>>> both
>>>>>> - if 1.0.0.0/8 is DOWN, R1 should not advertise 2.0.0.0/8 to R3
>>>>>> - if 2.0.0.0/8 is DOWN, R1 should only advertise net 1.0.0.0/8 to R3
>>>>>>
>>>>>> network 2.0.0.0/8 is dependent on 1.0.0.0/8. (second requirement).
>>>>>> 1st and third requirements are the default behavior of the BGP
>>>>>> process.
>>>>>>
>>>>>> Hence the solution only focuses on the second requirement.
>>>>>>
>>>>>> HTH,
>>>>>>
>>>>>> On 2/24/10, Ivan Hrvatska <ivanzghr_at_gmail.com> wrote:
>>>>>>> Hi experts,
>>>>>>>
>>>>>>> I have some difficulties to catch this scenario with BGP conditional
>>>>>>> adv:
>>>>>>>
>>>>>>> R1-----------R2
>>>>>>> |
>>>>>>> |
>>>>>>> R3
>>>>>>>
>>>>>>> R1 has lo0 1.1.1.1/8, R2 has Lo0 2.2.2.2/8 and R3 has also Lo0
>>>>>>> 3.3.3.3/8. All RTs are in same AS and all of them advertise their
>>>>>>> loopbacks.
>>>>>>> Task is next:
>>>>>>> - if both nets 1.0.0.0 and 2.0.0.0 are up, R1 should advertise them
>>>>>>> both
>>>>>>> - if 1.0.0.0/8 is DOWN, R1 should not advertise 2.0.0.0/8 to R3
>>>>>>> - if 2.0.0.0/8 is DOWN, R1 should only advertise net 1.0.0.0/8 to R3
>>>>>>>
>>>>>>> Solution on R1:
>>>>>>> acl 1 permit 1.0.0.0 0.255.255.255
>>>>>>> acl 2 permit 2.0.0.0 0.255.255.255
>>>>>>>
>>>>>>> route-map ADV per 10
>>>>>>> match ip add 2
>>>>>>> route-map EXIST per 10
>>>>>>> match ip add 1
>>>>>>>
>>>>>>> router bgp 100
>>>>>>> neighbor R3 adv-map ADV exist-map EXIST
>>>>>>>
>>>>>>> So, from my point of view this task should do next:
>>>>>>> - if 1.0.0.0/8 is UP (2.0.0.0/8 can also be UP) advertise 2.0.0.0/8
>>>>>>> to
>>>>>>> R3 (task asks you to NOT advertise)
>>>>>>> - if 1.0.0.0/8 is DOWN (2.0.0.0/8 can also be DOWN), do not advertise
>>>>>>> anything
>>>>>>>
>>>>>>> This solution is correct, but I don't get the logic?
>>>>>>>
>>>>>>>
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>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Best Regards,
>>>>>>
>>>>>> Tolulope.
>>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Best Regards,
>>>>
>>>> Tolulope.
>>>
>>>
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>>>
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>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>> --
>> Best Regards,
>>
>> Tolulope.
>>
>

-- 
Best Regards,
Tolulope.
Blogs and organic groups at http://www.ccie.net
Received on Thu Feb 25 2010 - 16:48:51 ART

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