[j-nsp] L3VPN advertises the directly connected subnet - why?

[Luis Ximenez Gomez]

Well, if you use the command "vrf-target import target:xxxx:yy" then
everything which is in your local VRF will be advertised via MBGP to other
peers with a matching RT.  <--- your connected subnet will go

In the other hand, if you use "vrf-export <policy>"  then more granularity
is available and you will be advertising exactly what your policy matches
and nothing else.   <--- your connected subnet will not go unless specified
in the policy.

Does this help?

Best regards, luis 

> -----Original Message-----
> From: juniper-nsp-bounces at puck.nether.net 
> [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of 
> Jeroen Valcke
> Sent: martes, 26 de enero de 2010 16:52
> To: juniper-nsp at puck.nether.net
> Subject: [j-nsp] L3VPN advertises the directly connected subnet - why?
> 
> Hi,
> 
> I'm doing some testing with simple plain L3VPNs and ran into 
> some weird behaviour. At least I think it's weird. Perhaps 
> somebody can enlighten me.
> 
> A CE router is exchanging routes with the PE through BGP. 
> These routes are correctly advertised 'over' the L3VPN 
> towards other CE routers.
> However the directly connected subnet between the CE and PE 
> is also advertised to the other CE routers. 
> 
> Why is this? It was my understanding that only the routes 
> learned from the BGP advertisement from the CE router would 
> be advertised to the other CE routers.
> 
> What's the reasoning behind this behaviour?
> Can I alter this behaviour? And if yes, is it safe to do so?
> 
> Weirdly enough I've found a Juniper KB [1] which seems to 
> document the exact opposite behaviour of what I'm 
> experiencing. This KB describes a case where the directly 
> connected subnet is not advertised over the L3VPN and how to 
> 'fix' this.
> 
> Thanks for any clues.
> Kind regards,
> -Jeroen-
> 
> PS: JunOS version on the PE routers is 9.3R2.8
> 
> [1] 
> http://kb.juniper.net/index?page=content&id=KB12430&cat=BGP&actp=LIST
> 
> --
> Jeroen Valcke
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