Re: Loop Prevention MPLS VPN

Hello,

This looked like an interesting scenario to test out so I did in dynamips.
I have a loopback (100.0.0.100/8) on PE3 being redistributed into vrf OSPF
with CE2 and into MP-BGP with PE1 and PE2. PE1 and PE2 are redistributing
from MP-BGP into OSPF vrf with CE1.

What I found was that while CE1 does have the ospf route for
100.0.0.0/8(type 5 E2 in the database) PE1 and PE2 are only installing
the MP-BGP route
in their routing tables. PE1 and PE2 do have 100.0.0.0/8 in their OSPF
databases though - they are just not installing it in their routing tables
for the vrf at all.

There may be something fundamental I am missing in this scenario or the
description, but there looks to be something inherent with MP-BGP and OSPF
that I don't yet know (rather new to MPLS L3 VPNs). Seems despite OSPFs
lower AD, the MP-BGP routes (AD 200) are still preferred on the PEs.
Logically this makes sense as a loop prevention mechanism though - I will
definitely research this more - but just throwing that out there if there is
further comment on it before I RTFM.

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Received on Wed Dec 01 2010 - 10:25:39 ART