From: Suryakant P (suryakant.pandian@gmail.com)
Date: Fri Apr 18 2008 - 11:34:56 ART
Hi Thomas,
In scenario 1 , Going by your explanation,the same logic should be used by
router A,isnt it?
But router A installs the N2 route in the routing table instead of the E2
route.
Does router A being the Type 7 - Type 5 converter could make the difference
here ?Or is it something else?
Thanks
With regards
Suryakant
On 4/18/08, Thomas Fowles <tfowles@gmail.com> wrote:
>
> Suryakant,
>
> In Scenario 1, both the N2 and E2 routes presumably have the same
> characteristics (forwarding address of router C, cost, etc). All things
> being equal, an E2 is preferred over an N2 route. So router B installs the
> E2 advertised by router A into area 0.
>
> In Scenario 2, when router A strips out the forwarding address, router A's
> area 0 interface becomes the next hop for the E2 route. At this point
> (judging from your sesults) the N2 route with router C as the next hop
> becomes more attractive than router A's area 0 interface as next hop.
>
> Here are a couple of documentation links that might clarify things a bit,
> although admitedly this can be a tough one to wrap your head around.
>
>
> http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080124c7d.shtml
>
> http://www.cisco.com/en/US/docs/ios/12_4/ip_route/configuration/guide/hoadsup.html#wp1037600
>
> HTH
>
> -Tom
> CCIE#18762(R&S, SP in progress, humbled daily)
>
>
>
> On Thu, Apr 17, 2008 at 8:32 AM, Suryakant P <suryakant.pandian@gmail.com>
> wrote:
>
> > Hi All,
> >
> > Routers A ,B and C are connected to the ethernet LAN network.OSPF
> > peering is
> > established between them and the area is configured as the NSSA area.
> >
> > Router C acts as the ASBR and Routers A and B have connectivity
> > to Area 0 and hence act as ABRs.
> >
> > I have made the router A as the type 7 to type 5 converter(by increasing
> > the
> > router-id on the A).
> >
> > Now when C advertises a network(by redistributing into OSPF),both router
> > A
> > and B receive the TYPE 7 LSA.
> >
> > A and B will have the TYPE 5 LSA generated by the router A.
> >
> > *Scenario 1 :* When the forwardaddress in TYPE 5 LSA is set to Router C
> > router id.
> > Router A installs N2 route in the routing table but router B installs E2
> > route in the routing table?Could you please explain the reason behind
> > the
> > selection of E2 route on the router B.
> >
> > *Scenario 2 :* When the forwardaddress in TYPE 5 LSA is set to
> > 0.0.0.0(suppress-fa configured on the converter)
> > Both router A and router B install N2 route to the network
> > advertised.Could
> > you please explain the reason behind the change in route selection once
> > the
> > forward has been suppressed.
> >
> > Thanks
> > With regards
> > Suryakant
> >
> >
> > Pass the CCIE in six weeks, Guaranteed!
> > http://www.certscience.com/CCIE
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