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

[Andy Vance]

Without config snapshots of the VRF, the import policy and the export policy, it is difficult to say why you see this behavior, I have some ideas but I don't want to guess.  Can you provide config snapshots?  I don't want to assume and head down some road that may not be relevant.

Cheers,
Andy Vance
Sr. Network Engineer
Speakeasy
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-----Original Message-----
From: juniper-nsp-bounces at puck.nether.net [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Jeroen Valcke
Sent: Tuesday, January 26, 2010 7:52 AM
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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