Re: preferring OSPF inter-area compared to intra-area

No need to lab it. I understand that no inter area route exists to be
installed in global. Was good discussion when blocking out the noise.
Thanks

Marc

On Tuesday, January 8, 2013, marc edwards wrote:

> Sorry, Brian. I should lab this up instead of just asking. Sometimes
> you guys make it too simple ;)
>
> cheers,
>
> Marc
>
> On Tue, Jan 8, 2013 at 8:39 PM, marc edwards <renorider_at_gmail.com<javascript:;>>
> wrote:
> > So what would happend if the Inter area route was set to lower distance?
> >
> > On Tue, Jan 8, 2013 at 3:45 PM, Brian McGahan <bmcgahan_at_ine.com<javascript:;>>
> wrote:
> >> You can use distance to filter, but you can't use it to prefer one
> route type over another. If you have an Intra-Area route and an Inter-Area
> route for the same prefix, the Intra-Area route is chosen as best and goes
> to the OSPF RIB. The distance is then applied to the OSPF RIB before the
> route goes to the global RIB, which is the routing table. The issue
> becomes that even if you poison the Intra-Area route by setting its
> distance to 255, it was the only route in the OSPF RIB to begin with, and
> the end result is that OSPF feeds no route to the RIB for that prefix.
> >>
> >> In other words you can deny OSPF from installing the prefix in the
> routing table overall, but you can't deny it from installing the Intra-Area
> route in order to get it to install the Inter-Area route instead.
> >>
> >> This is the same type of reason that Sham Links are implemented in MPLS
> L3VPN with OSPF as the PE-CE routing protocol, because if you're migrating
> off of a private layer 2 VPN service like Frame Relay to MPLS L3VPN, your
> Intra-Area routes over the Frame Relay network would always be preferred
> over the Inter-Area or External routes coming from the MPLS L3VPN. The fix
> is to run a Sham Link over the MPLS L3VPN which makes the routes be able to
> come in as Intra-Area. If you now have an Intra-Area route over Frame
> Relay and an Intra-Area route over MPLS you can just change the link costs
> so that the Frame Relay is used as a backup.
> >>
> >>
> >>
> >> Brian McGahan, CCIE #8593 (R&S/SP/Security)
> >> bmcgahan_at_INE.com
> >>
> >> Internetwork Expert, Inc.
> >> http://www.INE.com
> >>
> >>
> >> -----Original Message-----
> >> From: marc edwards [mailto:renorider_at_gmail.com <javascript:;>]
> >> Sent: Tuesday, January 08, 2013 4:45 PM
> >> To: ccie99999
> >> Cc: rakesh madupu; Jay McMickle; Brian McGahan; Narbik Kocharians;
> Carlos G Mendioroz; Cisco certification
> >> Subject: Re: preferring OSPF inter-area compared to intra-area
> >>
> >> Try using distance command under ospf process of R6 to manipulate path
> selection. I am surprised this wasn't suggested..... or did i miss it?
> >>
> >> Why don't you try using distance command under ospf process
> >>
> >> On Tue, Jan 8, 2013 at 12:19 PM, ccie99999 <ccie99999_at_gmail.com<javascript:;>>
> wrote:
> >>> Hi Rakesh,
> >>>
> >>> yeah.. I'm just filtering rib and not ospf db.
> >>> I've no idea of I could make an inter-area route become an intra-area,
> >>> using a route-map or a filter.
> >>> Best way is move the interface to the same area or use a VL I need to
> >>> lab it a bit.
> >>>
> >>> On Tue, Jan 8, 2013 at 5:19 PM, rakesh madupu <raaki.88_at_gmail.com<javascript:;>>
> wrote:
> >>>
> >>>> Rakesh
> >>>
> >>>
> >>>
> >>>
> >>> --
> >>> @ccie99999
> >>> https://twitter.com/ccie99999
> >>>
> >>>
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Received on Tue Jan 08 2013 - 22:16:08 ART