Go CCIE Go!! - A Cisco Certified Internetwork Expert

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 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 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″ To: Cc: “Cisco certification” 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