Re: BGP advertisement logic?

I don't know INE's Vol1 topo, a quick refresh of the involved links/ASs
would help.
In any case:
-sender is not supposed to apply receiver's policy by default.
That is, even if I know YOU are on AS100, I SHOULD send you updates with
AS100 inside, after all you MIGHT be doing allowas-in.
-receiver might negotiate filters to be applied (ORF) on the sender.
I don't know the timing of those, and may be they are involved ?

-Carlos

Keller Giacomarro @ 20/11/2011 06:48 -0300 dixit:
> While doing some of the INE Vol1 BGP labs with 'debug ip bgp *neighbor' *turned
> on, I noticed a strange behavior that I cannot explain.
>
> I am doing a hard reset between two peers. R3 is in AS200, R1 is in AS100.
> From the debug of reset on R3, what is happening is that R3 is advertising
> all of its prefixes to R1, then withdrawing all the prefixes that contain
> AS 100 in their AS_PATH.
>
> Full debug logs @ http://pastebin.com/raw.php?i=cRxBGbwm
>
> I understand the logic behind not wanting to advertise a route into an AS
> that is originated from, but doesn't R1 handle that too (DENIED due to:
> AS-PATH contains our own AS)? And R1 knows what AS R3 is in -- why is it
> sending the updates in the first place? Is there some other mechanism that
> is making R3 withdraw the routes it JUST sent?
>
> As I study for the lab, I'm trying to ensure I don't just know commands,
> but understand the guts of how the protocols work. Your insight is
> appreciated!
>
> Keller Giacomarro
> keller.g_at_gmail.com
>
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-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net