Re: EIGRP SOO

Gaurav Madan,
EIGRP SOO works as an explicit marker / implicit filter, both
on the BGP-EIGRP redistribution point (via vrf sitemap) and
at the backdoor links (also via vrf sitemap!).
The SOO mark is supported both in EIGRP and in MP-BGP (ext comm).

CE-PE:
Route coming from CE gets SOO checked. If same as this, it gets
filtered. If other, mark is passed to BGP, if none, it gets marked.
Route going to CE gets marked with incoming mark.

BR-BR:
Route coming in gets checked. Same ? Filter.
Route going to other site gets marked if not already.

Answers inline:

GAURAV MADAN @ 10/02/2011 03:55 -0300 dixit:
> 2nd try .. Can someone help me in understanding this
>
> Thnx
> Gaurav Madan
>
> On Wed, Feb 9, 2011 at 7:43 PM, GAURAV MADAN <gauravmadan1177_at_gmail.com> wrote:
>> Hi All
>>
>> I am reading MPLS fundamentals (Page 225) and I have following query :
>>
>> They have shown that SOO is added on PE router (PE-CE link) and on
>> backdoor interface.
>> My question is ; does this SOO attribute gets added to incoming as
>> well as outgoing EIGRP routes on that interface ?

Outgoing, yes if not already marked. Incoming... don't know,
they should all have markings anyway from wherever they come.

>> i.e. if my f0/0 has soo 1:100 .... does that mean all EIGRP routes
>> going out f0/0 will be tagged with soo = 1:100 and if any routes are

Nope, some routes may have a different SOO and it will go untouched.

>> coming IN f0/0 with soo = 1:100 ; these will be dropped ?

Yup.
>>
>> If possible ; can someone please explain the flow of how routing loop
>> is avoided in example given in book ?

The routing loop is created because you would have an "echo" of your
routes via the alternative path. It's a classic 2 way mutual
redistribution. Happens either with backdoor or dual homing.

SOO breaks it by not letting you go to some other part of a site via
a backbone link. (So if you have a site partition, you won't see an
alternative via the backbone).

-Carlos

>>
>> Many thanks in advance
>> Gaurav Madan
>>
>>
>> PS : I have also read the link
>> http://wiki.nil.com/Multihomed_MPLS_VPN_sites_running_EIGRP
>>
>> It states : The Site-of-Origin is an extended BGP community attached
>> to routes redistributed into MP-BGP from a PE-CE routing protocol. The
>> routes marked with a SoO are not advertised over PE-CE interfaces
>> having the same SoO,
>>
>> In the example given in MPLS fundamental book ; we are not applying
>> this SOO to routes going in MP-BGP . We are applying it on non-core
>> path itself . Can someone please explain .
>
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-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net