OSPF-NSSA

Unanswered Question
Jun 17th, 2007

Suppose i have three router ( R1---R2--R3) , R1 and R2 is in area 0 and R2 and R3 in NSSA , when i implement this in Lab, i am not getting R1 routes into R3, but i am getting R3's route in to R1.


why ?

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 3 (1 ratings)
Loading.
Richard Burts Sun, 06/17/2007 - 05:03

Vinod


Some details of how you have configured this OSPF would be helpful. The symptoms sound like you have configured NSSA with the no summary option. Using the no summary option will result in type 3 summary routes not being advertised into the NSSA area. Routers within the NSSA do not see individual routes from area 0 but use the default route to access all resources in area 0 (and in other OSPF areas if they exist).


So it sounds like that is what you have done. If you provide the configuration details we can confirm if this is the case.


HTH


Rick

Edison Ortiz Sun, 06/17/2007 - 06:47

NSSA prevents routes from entering the NSSA, it does not prevent routes from exiting the NSSA.


As Rick stated, NSSA provides different options such as: 'no-summary', 'no-redistribution', 'default-information originate' among others which can alter the default behavior of a NSSA.


A default behavior of a NSSA is to allow LSA type 1,2 and 3 into the area.



sundar.palaniappan Sun, 06/17/2007 - 08:00

Vinod,


It's hard to say for sure what's causing your problem without looking at the rotuer config(s) or some other show command output. However, the problem you describe may be a result of nssa forwarding address problem. Take a look at this link for more info on what it means and whether this is the reason for your issue.


http://cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a00804556e5.html


If this link doesn't help or if you are still having issues then please share the config of all 3 routers.


HTH


Sundar



Actions

This Discussion