Re: MPLS VPN Design and BGP SoO

YUP!!!!!

Paul Negron
CCIE# 14856
negron.paul_at_gmail.com
303-725-8162

On Oct 8, 2012, at 1:59 AM, Karim Jamali <karim.jamali_at_gmail.com> wrote:

> Hi Keller,
>
> You are right on this..To make it plain & simple:
> 1)In regular scenarios where different ASN numbers are used for the
> customers,BGP uses AS_PATH for loop prevention thus there is no point of
> using BGP SOO or any form of community to do the ftilering as AS_PATH
> automatically takes care of it.
> 2)When you are using the same ASN on customer sites, then BGP AS_PATH will
> not be used for filtering. Thus, BGP SOO or any other community can be used
> to tag/filter routes.
>
> Thank You
>
> On Mon, Oct 8, 2012 at 10:25 AM, Keller Giacomarro
<keller.g_at_gmail.com>wrote:
>
>> Hi Karim,
>>
>> That supports what I was thinking -- the only time you would ever need to
>> use BGP SoO is when you have multiple sites using the same BGP ASN and
some
>> of them are multihomed. In that case, you would have to do either
>> 'as-override' or 'allowas-in', but you wouldn't want to have routes enter
>> via one PE and then get re-advertised via the other PE. So, we use SoO to
>> prevent these looping updates from being re-accepted into the
>> originally-advertising site.
>>
>> Is that about right?
>>
>> Keller Giacomarro
>> keller.g_at_gmail.com
>>
>>
>>
>> On Mon, Oct 8, 2012 at 2:22 AM, Karim Jamali
<karim.jamali_at_gmail.com>wrote:
>>
>>> Hi Keller,
>>>
>>> The only scenario I have came across is suppose you have two sites one is
>>> dual homed to two PE routers and another site connected to a third PE
>>> within an MPLS VPN using the same AS. When you use as-override for
instance
>>> routes can be propagated between sites. Thus we have a problem that a
route
>>> originated within site 1 can go to PE1 to PE2 which will do the
as-override
>>> and send it CE2 within the same site. Thus the BGP SOO or any community
can
>>> be used to filter this behavior.
>>>
>>> Thanks
>>> On Oct 8, 2012 10:11 AM, "Gaurav Thukral" <pearlgaurav_at_gmail.com> wrote:
>>>
>>>> Hi Keller
>>>>
>>>> It's my fault. Let me go through the requirement.
>>>>
>>>> Thanks
>>>> Gaurav
>>>>
>>>> On Mon, Oct 8, 2012 at 12:24 PM, Keller Giacomarro <keller.g_at_gmail.com
>>>>> wrote:
>>>>
>>>>> Hi Gaurav,
>>>>>
>>>>> I have read through that doc, and it addresses EIGRP SoO only. My
>>>>> questions are specifically about BGP SoO.
>>>>>
>>>>> Keller Giacomarro
>>>>> keller.g_at_gmail.com
>>>>>
>>>>>
>>>>>
>>>>> On Mon, Oct 8, 2012 at 1:48 AM, Gaurav Thukral <pearlgaurav_at_gmail.com
>>>>> wrote:
>>>>>
>>>>>> Hi
>>>>>>
>>>>>> Kindly go through the below doc.
>>>>>>
>>>>>>
>>>>>>
>>>>
http://blog.ine.com/wp-content/uploads/2010/04/understanding-eigrp-soo-bgp-co
st-community.pdf
>>>>>>
>>>>>> Thanks
>>>>>> Gaurav
>>>>>>
>>>>>> On Mon, Oct 8, 2012 at 9:48 AM, Keller Giacomarro <keller.g_at_gmail.com
>>>>> wrote:
>>>>>>
>>>>>>> I am having issues understanding when to use SoO where. These are
>>>> the
>>>>>>> scenarios I can think of where we'd be using BGP as the IGP and would
>>>>>>> consider the use of some of these more advanced BGP multi-homing
>>>>>>> features...
>>>>>>>
>>>>>>> Two sites, different ASNs, no backdoor link
>>>>>>> - no special config needed
>>>>>>>
>>>>>>> Two sites, same ASN, no backdoor link
>>>>>>> - use either allowas-in or as-override to allow the sites to accept
>>>>>>> routes
>>>>>>> from each other
>>>>>>> - if any of the site are multi-homed, use SoO to keep the routes from
>>>>>>> circling back into the same site via the other PE
>>>>>>>
>>>>>>> Two sites, different ASNs, with backdoor (backup-only) link
>>>>>>> - peer the backdoor CE routers via eBGP and prepend to prefer the
>>>> MPLS
>>>>>>> link
>>>>>>>
>>>>>>> Two sites, same ASN, with backdoor (backup-only) link
>>>>>>> - ???
>>>>>>>
>>>>>>> One site, one ASN, multiple MPLS exit points, with intra-site active
>>>>>>> (non-backup) links
>>>>>>> - no special config needed, but MPLS cannot be used if the internal
>>>> site
>>>>>>> becomes segmented (due to AS_PATH loop prevention)
>>>>>>>
>>>>>>> First, are the above designs correct?
>>>>>>>
>>>>>>> And second, what is the proper way to setup "Two sites, same ASN,
>>>> with
>>>>>>> backdoor (backup-only) link"? I put it into GNS3, and I can't get
>>>> the
>>>>>>> traffic to prefer the MPLS backbone instead of the backup (iBGP)
>>>> link.
>>>>>>> The
>>>>>>> PE routers both prefer the eBGP link towards the internal network,
>>>> and
>>>>>>> neither will accept the (preferred) iBGP ad from their peer PE
>>>> router.
>>>>>>> It
>>>>>>> works fine going the reverse -- backup link works great, and if the
>>>>>>> backup
>>>>>>> link goes down the MPLS core is used.
>>>>>>>
>>>>>>> The only way I can figure to get the desired "MPLS primary, backdoor
>>>> link
>>>>>>> is backup" behavior is to do some kludge between the CE routers so
>>>> that
>>>>>>> they only advertise the routes to each other if the MPLS network is
>>>> down.
>>>>>>>
>>>>>>> Is the only time you want to use BGP SoO when all your sites are on
>>>> the
>>>>>>> same AS (forcing allowas-in or as-override), and some are multihomed?
>>>>>>> Otherwise, won't BGP AS_PATH loop prevention prevent the looping?
>>>>>>>
>>>>>>> Very confused, appreciate your input!
>>>>>>>
>>>>>>> Keller Giacomarro
>>>>>>> keller.g_at_gmail.com
>>>>>>>
>>>>>>>
>>>>>>> Blogs and organic groups at http://www.ccie.net
>>>>>>>
>>>>>>>
>>>> _______________________________________________________________________
>>>>>>> Subscription information may be found at:
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>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Thanks & Regards,
>>>>>> Gaurav Thukral
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Thanks & Regards,
>>>> Gaurav Thukral
>>>>
>>>>
>>>> Blogs and organic groups at http://www.ccie.net
>>>>
>>>> _______________________________________________________________________
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>>>> http://www.groupstudy.com/list/CCIELab.html
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>
>
>
> --
> KJ
>
>
> Blogs and organic groups at http://www.ccie.net
>
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Received on Mon Oct 08 2012 - 08:56:53 ART