From: Alex (alex.arseniev@gmail.com)
Date: Mon Jul 31 2006 - 10:03:53 ART
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009405a.shtml#t3
RFC 2328 , section 16.4 (Calculating AS external routes), states:
"If the forwarding address is non-zero, look up the forwarding address in
the routing table. The matching routing table entry must specify an
intra-area or inter-area path; if no such path exists, do nothing with the
LSA and consider the next in the list."
So if forwarding address is non-zero and is not covered by "network"
statement under "router ospf" section then it is not inserted into routing
table. In Your case if the R1-generated Type-7 default route has a
forwarding address which is set to the IP address belonging to R1-R3 subnet
and R3 has "network" statement for area 100 with 0.0.0.0 mask then this is
technically a connected route and not OSPF route. I believe it is true for
both Type-7 and Type-5 routes.
HTH
Cheers
Alex
----- Original Message -----
From: CCIEin2006
To: Alex
Cc: Cisco certification
Sent: Monday, July 31, 2006 12:10 PM
Subject: Re: Tricky One - Can Backbone router learn default route from NSSA?
Thanks Alex - Unfortuantely my rack time is over so I cannot show any
outputs.
But what is wrong with having a "connected" route towards the forwarding
address? Is that documented somewhere?
On 7/31/06, Alex <alex.arseniev@gmail.com> wrote:
I wonder if it might be a same problem as with "regular" OSPF default
routes: the OSPF router must have an internal OSPF route to the forwarding
address.
That means, if R3 has a "connected" route towards forwarding address of
R1-originated default and R3 is configured with "network <blah> 0.0.0.0"
statement
then R3 won't pass default to own routing table.
Need to see Your configs and "show ip ospf database nssa" printout from R3.
HTH
Cheers
Alex
----- Original Message -----
From: "CCIEin2006" < ciscocciein2006@gmail.com>
To: <swm@emanon.com>
Cc: "Cisco certification" < ccielab@groupstudy.com>
Sent: Monday, July 31, 2006 11:38 AM
Subject: Re: Tricky One - Can Backbone router learn default route from NSSA?
> Basically the setup looks like this:
>
> (R1)--Area100--(R3)--Area0
> |
> Area100
> |
> (R2)
>
> R1, R2, and R3 are connected to Area100 which is a NSSA. R3 is also
> connected to Area0.
> R1 is configured with Area 100 nssa default-information-originate.
>
> Both R2 and R3 see the 0.0.0.0 route in their OSPF database but only R2
> actually enters the route in its routing table. R3 is not entering the
> route
> in its routing table.
>
> Can you explain why that is? I figured it might have something to do with
> R3
> being connected to Area0 but I'm not sure....
>
> Thanks
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