Re: OSPF filtering

Ivan,

The design you selected "against" the rules of OSPF multi-area
routing. However, a very similar situation is often faced in
multihomed MPLS/BGP VPN OSPF scenarios. The solution used there is
known OSPF sham link. However, essential features needed for the sham
link are the MPLS LSP available to tunnel packets between the
connecting ABRs and BGP VPNv4 prefixes propagation (actual routing is
done based on BGP forwarding information).

As an equivalent solution for an IP-only network, you may consider
running a Layer 3 tunnel between Area 212's ABRs and across Area 0
configuring it as an Area 212 link. This will automatically make any
paths calculated for Area 212 across the tunnel seen as intra-area
routes for Area 212 routers. By adjusting the tunnel OSPF cost you may
steer traffic to flow across the backbone area. The tunnel is
necessary as backbone OSPF routers (non Area 212's ABRs) may have no
idea about topology for Area 212.

Naturally, this solution has some drawbacks from both design (topology
is less clear and harder to troubleshoot) and implementation
standpoint (e.g. MTU issues). You may also consider other tunneling
options, e.g. layer 2 tunnels or layer 2 PVCs between the ABRs (if the
underlying infrastructure supports that).

HTH

-- 
Petr Lapukhov, petr_at_INE.com
CCIE #16379 (R&S/Security/SP/Voice)
Internetwork Expert, Inc.
http://www.INE.com
Toll Free: 877-224-8987
Outside US: 775-826-4344
2010/1/22 Ivan Hrvatska <ivanzghr_at_gmail.com>:
> Anybody?
>
> On Fri, Jan 22, 2010 at 4:15 PM, Ivan Hrvatska <ivanzghr_at_gmail.com> wrote:
>> Hi,
>>
>> I have situation (see pic) where my traffic goes through backup links
>> because it is same area. It should go through area 0. I cannot change
>> the fact that area 212 is stub and I cannot influence on areas. What
>> can I do to make traffic goes through area 0 between Location 1 and
>> Location 2? In area 0 ABR routers summarize networks and filter out
>> only summarize networks originated in Area 0. Also, they advertise to
>> Location 1 only summarized route to Location 2 and vice verse.
>> My question is how can I manipulate in this design so that transit
>> through area 0 should be PRIMARY and through ME backup only if primary
>> fails.
>>
>> Regards
>
>
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