[j-nsp] Independent domain

[David Ball]

  Here's how I would nutshell it.  You have a customer VRF whose AS is
1.  They advertise routes to you via iBGP. Your core network (the
primary routing instance) uses AS3.

  Without independent-domain configured, if the customer advertises
10.0.0.0/24 to you via iBGP, it'll have their AS1 in the AS path, but
to transport the advertisement across your core to the other PEs where
they connect, your core AS3 is added to the AS path by MP-BGP (AS path
is now  3 1).  When it comes 'out' of the core back into the L3VPN at
a remote PE, the L3VPN AS1 is added again, making the AS Path  1 3 1,
which is an AS Loop.  Similar happens if they're doing eBGP with you.

The independent-domain knob ensures that only the ASes in the
routing-instance are checked during loop detection, and the
main/primary routing instances (your core's AS3) is not considered.
By default this is done, per the docs, by using transitive attribute
128 which hides the route's as path, LP, etc in the AttrSet so those
attributes are hidden away during the loop checking.  In newer code
(10.3+ ?) you can use the 'no-attr-set' knob following the
'independent-domain' knob which doesn't use AttrSet and simply does
loop checking on routing-instances ASes without considering your
core's AS used in MP-BGP.

HTH,

David



On 27 July 2011 01:05, biwa net <biwa2go at gmail.com> wrote:
> Dear All
>
> I am having a hard time understanding the concept of "independent-domain " ,
>
> Although I read the doc about it , the explanation, is not very clearly
> explained and not very clear in practical terms
>
> Anyone can explain in leman terms what is the role of it , and especially
> can anyone give me some real life example where and how this would be
> applied ?
>
> Thanks
>
> Biwa
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